Nobody is making replacements for those drums, and they're extremely scarce and expensive when serviceable used ones can be found. Wheel cylinders are still available, and the shoes can be relined or replaced. As long as the drums aren't badly scored or machined way oversize, it's best to reuse what you have. I believe the usual maximum oversize is .090", but I've seen them work well when machined as much as 1/8" oversize if the linings are radius-ground to an exact fit with the drums. A shade tree method of doing that is to glue a piece of coarse sandpaper to the inside of the drum and scuff the linings to a close fit. Using water-based glue like wallpaper paste makes the sandpaper easier to remove.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!