Two kinds of sellers there, the mega-seller, and the "I've got some stuff I need to get rid of and somebody might pay me a couple of bucks for it" seller. I've done well with both kinds of people, most of the former category are just independent entrepreneurs. In fact, as the retail outlets close, the only way to find parts or accessories for things that we've already got is to go to eBay.
Don't forget flea markets and the often scowled upon art of the dumpster dive. (it's not just for leftists anymore.)
That's funny, I was just thinking this weekend that we're going to have to adopt techniques that the Abbie Hoffman "Steal This Book" types were using forty years ago to try to end the Vietnam War! The only difference is that they were never going to be productive members of society, they were always going to suck off of a government teat no matter how things went, and we are the people who really produce things and make the world work. Our shutting down will have a much greater effect than the hippies dropping out.
Good luck with the garden! I'm going to see if I can get a couple of half whiskey barrels for the back deck to grow some yellow Finnish potatoes, I don't think the condo association would let us get away with anything less froo-froo!
A good place for survival equipment is RangerJoes.com
They have a lot of military and SWAT grade items and are fairly reasonable in price.
The less of a trail the dogs have to follow to your wallet, the less you're going to have to feed them.
As I see it, if there's absolutely no other choice but to bid on an item you can't get anywhere else, sure go ahead, but it should be a last ditch effort to get something you can't possibly live without.
We have a set of Foxfire books. Interviews and how-to manuals on independent rural mountain living in the old days. Copies of the Foxfire series may be available on-line or on ebay. They were published during the 1970’s.
I bought green vinyl chicken "wire" at Lowes - $12 for a 3' by 25' roll that I figure will make five potato bins which I'll hold together with ty-wraps.