If you've ever had a GFCI trip because of moisture around the plug, you'll appreciate the Protect- A-Plug weather-protected outlet cover (Intermatic, Intermatic Plaza, Spring Grove, IL 60081; 815/675- 2321). The backing plate mounts on single or double-gang electrical boxes, in either a vertical or horizontal position. Two plastic coverplate inserts fit either duplex or GFCI outlets, and a clear plastic cover closes against a gasket to seal moisture out. The cover hinges at the top for easy access to the plugs, and the power cords exit through a slot in the bottom. The Protect-A-Plug is available in two different cover depths, one for 14-gauge and smaller cords and another for 12-gauge or larger cords. Cost ranges between $20 and $45. If you leave