About 30 years ago I couldn't find the right gasket and didn't have enough material to make one, so I cleaned both surfaces well and applied RTV sealant (silicone some would say) around the cover about 3/16 thick in 2 lines spaced about 1/4" apart, making circles around each bolt hole. Let it sit there for 10 or 15 minutes...followed the directions on the tube...and then installed the cover. It never leaked a drop after that and the tube of sealer cost me about $6 or $7. Good luck.
