I'm not sure they always used the same spars all the way through a production run. Often, the same mast and boom extrusions were used on different boat. They were just cut to the correct length. I have an oval boom that came from a Pearson 26 that might be about the right size.
Is your boom round, or oval?
Try looking at
www.rigrite.com for parts. You may be able to match by size and shape.