call the catalina factory.
(not the same as catalina direct). Their phone number is on the website http://www.catalinayachts.com. Ask for the parts dept. If you have all the hardware, you just need the spar itself. The big cost is in the fittings, so salvage what you can from your existing rig and only order what you need. Go to the catalina 27 international website to find drawings of the boom and it's dimensions.Go to the factory first, in all instances, when you have a parts need. Chances are you'll find it there, cheaper. The Catalina 27 is well supported by the factory even though it's been out of production for well over 10 years.