Yep, what OS9Dude said. I see a bunch come up on eBay, along with VIC-20s. Not always priced appropriately, but there are quite a few. You can set up an automatic daily search at eBay which will email you the results; it's pretty handy.
Check ShopGoodwill.com, and Craigslist. You can use one of the many Craigslist automated search tools to help.