I don't know that boat specifically, but when I need mast hoops for old school sailboats, the first place I look is the PVC pipe bins at Home Depot. Often PVC pipe comes in diameters that are close enough to cut rings out of. I have made my best looking rings on a lathe, but I have also made acceptable ones with a hack saw & a file. It's not that hard to do.
You can also cut them out of a flat sheet of plastic (like a cutting board) using 2 hole saws of different diameters.
Sail makers often know where to source them from commercial suppliers.