Welp, finally got batteries! here you go! not sure if you can see that the spray pain I used is causing black marks, but the case I bought for $25 wasn't all that chop anyway, and hey it's functional, next time I think I'll only spray the grey NES part instead of trying to make the whole damn thing look factory. I'd like to spray the NES part black and put it in one of those red controllers with the black trimmings, I think that would look sweet.
One of these look like a good option for this mod too but I could be wrong.
OK, so here are the pics;
Before Painting

Finished product

Close-up, notice the flaw

Two rubber dome things, the broken one I got in the NES, and the one I used instead

Back of shell, where I soldered the ground, also you can see some of the chips in the casing
I just realised some of my drawings got into the shots, lol hope you enjoy them.