It's from Ron and Stan, West Marine sells it:
https://www.westmarine.com/buy/ronstan--spinnaker-brace-hook--2500122A suggestion, look at Phill Root's "Rigging a Winning Daysailer" page on the our parent daysailer.org site. Instead of using a guy hook on deck, Phill simply puts a pulley sheave (actually, a becket roller, small sheave) on the outboard side of his chainplates. I think it's a more elegant solution - the guy stays put when the pole is forward and pops out when it's back, then auto-releases when you jibe. As Phill writes: No more trips to leeward to release a forgotten line.
Alternatively, there is this:
https://www.amazon.com/Stainless-Ceiling-Hangers-Straps-Rigging/dp/B07HVNMLKX/Stainless, just put a backing plate under it, and use a nut and bolt to fasten.
Anyway, all the best with the rigging project!
Tom