I found my KTMA Gypy seat in a thrift shop... so I guess it's possible.
Related story: In 1999 there was a convention in St. Louis that had Mike, Kevin, Bill, and Mary Jo as the guests.... some guy in the vendor area had TONS of original bot parts for sale... he must have had 20 Century car seats. I asked him where he got them all, he said he'd been to every Goodwill between St. Louis and Chicago to find them all.... if memory serves he was asking $25 each. I wasn't a bot builder at the time, so I didn't realize that I should have bought every last one...