So I found that the big orange home improvement store carries gamma lids in the paint department, about 8 feet away from the 5 gallon pails. Close enough, I guess. The printed instructions mention the potential need for a mallet. Most of the write-ups and videos I've seen also mention the need for a mallet. Forget that. Use your butt. No, really. Put the lid on the floor, upside-down. Put the pail on the lid (also upside-down). Slowly sit down on the pail, assuming you'll probably have to do some plastic-pushing to get the pail lip and the lid to mate up properly. Then slowly lean forward, tipping the pail forward. When you get some weight on that point, the pail will simply snap into the ring of the gamma lid. Then lean all the way around in a circle to get the rest of the pail's lip to snap into the ring. No mallet. No cursing. It just works. The lids run just under $7/ea. They have a couple of different kinds of pail. They were out of the cheaper orange ones. The white ones run just under $4/ea. I make no claims that they have the lowest price, but if you value buying your supplies with cash and leaving no trace, they've got you covered. I've also found that a number of supermarkets are willing to give discounts for buying foods in bulk. No shipping costs, you pay cash, leave no record that you were ever there. You do pay state/local sales tax, though (if you live in an area that has it).
Product Review: Gamma Lids : The Food Storage Shopper If you're going to store food in buckets, and expect to eat regularly out of your food stores, it will make your life a lot easier to have them.