I looked at Autozone, O'reilly and Rockauto. All three have a less than $40 OBDII scanner that can get you started. All of them will read most codes on any vehicle.
If you are still working with OBDI, that might be a little harder to find. Even back when that was "State of the art", they were very clunky. I just broke out my old unit for an '89 Fox Body that was given to me. And, even though I was staring at a CEL, the scanner showed I had no codes. Go figure! Before I attempted the manual method of getting codes, the CEL turned off and went away. Guess I'll have to put a few miles on it to see if the light returns.
