It's simple, really: You just. Keep. Trying.
Most of what we really think of as 'retro' is largely in the collector's market now. If you want it in the wild, you have to cast a wider net, and be prepared for lots of disappointment. You check all the secondhand shops. You turn by every sign that says 'sale' with an arrow pointing to a stranger's house. You browse craigslist & other online local selling sources.
But most importantly- you don't let the internet get to you. It will convince you that good stuff is everywhere when really, it's one guy making one find 100 miles away from you, and he won't post again this year. You're seeing the collective finds for massive geographic regions condensed into one tiny space.
For me, personally, Two things help: 1) redefine what you're looking for. You don't find desirable, valuable things in these kinds of places- you find the stuff nobody wants right now. If you hit up the thrifts looking for NES/SNES, you will be sad. But now is a great time to find Wii, Xbox 360, and PS3- because right now those are 'old', not 'retro'. 2) Check gaming shows if you have any nearby. It sounds counterintuitive, but some of the best finds I've had the last couple years have been at retro expos. See, for the general populace, popular old titles (think Mario) are still something they want & can't find easily. But most retro collectors have their Marios already- so if you still need something like that, a retro show might cut you a deal becuase their customer base isn't buying that. And if you want causal fare? Dirt effin' cheap. I paid a dollar for a Wii Fit board last year at a retro show- a dollar! The thrifts want ten! The yard sale wanted $20! Then another seller saw me carrying it, and gave me a free Zumba Fitness CIB- he didn't want to haul it home! That was a good day.
