You're best bet is the goodwill stores, kitchen supply, or maybe even a dollar store.
Yeah, I might head into the Salvation Army right now. I'll check out the thrift stores while I'm out in Seattle too.
Wouldn't it make a better presentation if you had a few dozen that were all the same?
I'm really into the hodge-podge look when it comes to coffee cups. I love when I go into a cafe and they have a mixture of different coffee cups. Same with restaurants and plates.
Also, I'm a big proponent of sustainable practices. Reduce, REUSE, Recycle