Hunter,

Head back to WalMart--at least our local store has them, whatever they are called. Yellow, with 3 little dingie lights in a left to right row--green yellow and red? Color is not important. The code is printed on the yellow 3 prong plug in. If all 3 light up, you're OK; if a certain one is out you have a ground fault. Another combination indicates reverse polarity, etc. etc. They are also available at RV supply stores. About 1 1/2 inches wide, maybe 2 1/2 inches long, 3/4 inch thick.

Donald