As I've mentioned (bragged) in a couple other threads-- I went to a photo swap meet and bought a box of flashguns for $25... in 1994. I just wanted the Graflex in the box, but the guy insisted I take all his "junk." I ended up with a Graflex, 3 Heilands, and 5 or 6 other flashes (unsure what models, but will know soon as it's been recovered from mom's basement).
Just one year later I saw the guy again, and he knew what he had. In 1995 he wanted $50 for a single Graflite and I was like-- no way dude. Ha!
I can only imagine that these days he wakes up in a cold sweat, dreaming of a 20 year old me walking off with a box of "junk" that would easy fetch a couple thousand dollars today.
Ebay is pretty much the main game in town for finding stuff. It's amazing for that-- but it also sucks because people can see trends and you get a Canon X and Y situation where things that cost $20 a couple months ago are now going for close to $100.
Etsy actually has a good amount of resellers.
I've had a fair amount of luck from used camera shops-- either in your area, or online. I've found cool stuff by finding sellers on ebay that are shops, and then going to their website. A lot of them will be selling a ton of junk directly from their own sites, or you can even call them.
And photo swap meets still happen.
That said, photo peeps are pretty much all hip to the lightsaber scene. You can get random flashgun brands for custom sabers cheap, but unless you manage to stumble into some antique store or flea market in the middle of nowhere run by a clueless old lady with no internet, scoring a Graflex, Heiland, or MPP on the cheap is next to impossible.