Ugh, this thread made me go down a rabbit hole and I ended up bidding on a C64C on eBay. (I had a C64 as a kid but sold it to be able to afford an Amiga 500. No regrets.) Amazed at how much of a market there still is! Now I need to figure out how to connect it to a modern display, but this same web site has a pretty cool buyer's guide for that kind of stuff.