www.pemivalleyhabitat.org in Plymouth, the ReStore, almost always has a few different used garbage disposals for sale.
They maybe come from an olde Lake Winnipesaukee tear-down, or somewhere, when someone super-rich from New Jersey or Connecticut moves in and builds a new mcmansion on ye olde waterfront, same spot.
For five dollars about two years ago, I got me a Badger InSinkErator 1/2-hp and went and replaced the old InSinkErator 1/3-hp that had a worn bearing and it would sometime pop the red breaker button.
About that time, ReStore-Plymouth got a new manager, who is actually a paid employee and not a volunteer, and she has increased all the prices on everything by a whole lot. So today, my $5-bargain used InSinkErator would probably run about $35-40, and it would cost $110-new at a store.
www.Walmart.com has very good prices on new disposals that get shipped to you.