They are pretty common and reasonably priced - I bought an Actron CP9145 - about a $200 unit I bought just before I also bought the "Smarty" that has it's own code reader and eraser. I've only used the Actron twice, it's like new, and I'd sell it for $125 including shipping to anyone interested...
Most major auto parts should have a good unit for your needs, including NAPA - do a Internet search on OBDII readers, and also check Ebay for some good prices.