The floats are a closed cell foam plastic. these aren't the same material that they used in old Q-Jets, these things don't get fuel-logged.
I thought about brass, and it still might be an option, but good luck finding a brass float in a junk yard!, for that matter, good luck finding a float at all... if I use brass i'll fab it out of very thin brass from the hobby shop, but i'll probably start with balsa. there are different grades of balsa, based on weight, and I can carve with a dremil better than I can bend & solder brass. plus it's cheaper. for $3 I can get enough balsa to make several floats.
Hmm, plaster mold... messy & possably destructive to the good float. if I went that route I think I'd go with an epoxy mixed with glass mat fibers though.