Honestly, my favorite wind indicator is a good cigar, preferably a Double Toro or larger. On light wind days, the smoke shows you exactly what the wind is doing, especially if you blow it over the mainsail. For heavy wind (and spray) days, you're too busy keeping the damn thing lit to care about the wind direction, besides direction is kind of obvious from the whitecaps. Unfortunately, present health conditions preclude cigars, but one can dream

In the meantime, I've been using a Davis Windex 10, I think that's what most folks do. Perfect size, very visible, and has those nifty little tracking tabs. If you've never used those, when the tail of your windex arrow is on the tab, you're as close hauled as you can get (30ish degrees or so, really pinching). Inside the tabs you are in irons. A bit outside the tabs (40 to 45 degrees) is ideal. Vice versa when you are going downwind, if the point of the arrow is inside the tabs, you'll be wing on wing.
That being said (writ), you have to screw the holder for the windex to your mast somehow, no way around it (I'll give you some nonwindex options below). I'm a trailersailer, which also means that the windex has to come off (unscrew from the holder) whenever I take the mast down, otherwise guaranteed broken windex. Also, trees at the launch site and windexes don't mix (ask me how I know?).
Truth is that the masthead indicator is nice to have, not need to have. I bought a new windex after the unfortunate tree incident, and haven't put it up yet. There's so many other ways to read the wind, without having to crane your head up and take your eyes off the water and your sails (where you should really be looking). Waves are my primary wind indicators, the ripples are always at 90 degrees to the wind. But which waves? the big ones or the little ripples on top? What about during a shift? You'll soon learn, grasshopper! That's the fun of sailing. Most of the info that i get is from the telltales on the sail. Am I too close to the wind? The windward telltales on the jib will tell me. Read GreenLakes "Basic Concepts" here:
https://forum.daysailer.org/forum/viewtopic.php?f=43&t=6280.
Since this is my favorite forum, I'll tell you my "secret" advanced wind indicator — my ears. It helps that I have a shaved head, but what I do is simply turn the my head till the wind pressure and noise is the same on both ears. Then I know that I'm either facing directly upwind or directly downwind (depending if the wind is on the front or back of my ears). You may laugh, but it works perfectly, with the telltales for any finetuning. I learned this from my barber, of all people... Yes, despite a shaved head, I still go to the barber to trim up all the stray hairs and keep my beard neat. One day I complained "How comes I can't grow any hair on my head but it's growing even more on my ears?!?" and he said "That's so you old men can sense the cold wind when Death approaches..." That'll teach my for getting my beard done by a 30year old, but he has a point.. those little hairs are perfect for feeling the wind! I'll try and avoid the Grim Reaper, though.
Anyway, I digress. Look, those Laser strap—on indicators are too small to get on your mast and impossible to use if you have external halyards. If you want to experiment with a masthead indicator, just get yourself a small flag or streamer and bungie or rubber band it to the very top of your mast. You won't have the little tabs, but is just as good for seeing the wind as a windex. Like so:

- pennant.JPG (55.96 KiB) Viewed 15170 times
For that matter, you can put a bit of ribbon or telltale tape up there, harder to see but still useful. Likewise, try putting indicators on your side stays. Going upwind, the indicators should fly parallel to your mainsail, actually the other way around.. trim your main to match your side stay indicators. Again, can be a bit of tape, wool, ribbon, whatever, but I treated myself to these (on some super sale, of course):
https://farleyoutdoors.com/boating/outfitting-maintenance/marine-instruments/instruments-wind/davis-wind-tels-2-pack/Anyway, all kidding aside, seeing the wind direction is a matter of experience and time on the water. Any and all inputs are valid and will help you "build a picture" of what's happening. You'll soon learn that the wind at your deck level can be quite different from the wind at the masthead and you'll learn how to react to it. Wind comes in gusts, in vortexes, will roll over vertically like a crashing wave, will fan out, will bend around points of land, and blast thru gaps in the shoreline... it's truly three dimensional and can be as complex as a pot of boiling water. There's a LOT going on and no one instrument, be it your ear hairs or a windex, will tell you everything, you need to use all your senses. I'll leave you with one last trick (which I learned from my father, some 50 years ago), go "sailing" when you are walking around town. Try and see the wind swirling down the street, around buildings, across the fields, and then mentally set your imaginary sails to the correct trim. If you can, "tack" upwind as you walk, think about how you'll round the next corner, etc. Sailing is 90% mental , and the other half is physical (thank you Yogi Berra). You may not be on the water but you can always be training your eyes, your senses, your mind. Those are the best, true wind indicators.
Fair winds!
Tom