Try this link.
http://boonedocks.net/daysailer_old/index.html
That site and this site you are currently on are melding, so eventually all the info will be here. On the old site however, you want to click on parts and accessories then click on D & R Marine then oday models, then daysailer, then spars to see a replacement boom.
It is $295 for a complete boom, or 165 for the extrusion only, if you have all the old hardware from your old boom.