i have not removed that cover in years, you might be able to find different sizes at the auto parts store or maybe ace hardware if you have one around.Ok those are safe to use on that harness? Those are the ones I have had troubles with in the past. I think it was cause I was using the wrong size though maybe. What size wire is it do you know by chance from when you did it?
I have a couple wires tapped in there and have just let it be and have not had any problems so far.