"And yes... I picture removable tops on hollow metal pucks that can be filled with pellets to use in the Bradley puck feeder."
Now that I think of it....I will bet there are "lozenge tins" that are metal, and about the right diameter...If you can find some that are the right size....and you drill a couple of holes in the top, and one really small one down low on the side.... and you load up 8 or 10 of them.....might be the ticket ....