Ya know the boom on my C2 isn't much more than a 2" iirc piece of Aluminum tube (1/16" wall) with a few well located holes and slots... You probably can move the hardware from your old boom. Alu tube is cheap. Find a metal supply place near you. In LA, 20'of 2" tube is about $50.00 for 1/16 wall and $65 for 1/8" wall. Shorter lengths are usually cheaper even when they charge for cutting.
Pick something about the width of what you have and use a similar wall thickness.
If you use center boom sheeting, you might want to go 2.5"
Yeah, you could annodize, but that will add a minimum of $75 or so to the cost and not make a big difference in longevity.