If you are a N64 collector, modder, or simply like import games, you know that in order to play Japanese games on NTSC systems (or vice versa) require you to cut some of the plastic of your cartridge slot to play said games. I've done it before, I know. And I find it rather ugly. Besides, there is the probability that you might hurt yourself in the process. This is why I made this. Simply remove your existing cartridge slot and replace it with this one. It's that simple!
in case you don't have a 3D printer, here is the shapeways link: http://shpws.me/wprv
I had to set this to meters on the shapeways website for the dimensions to be accurate to the dimensions in the 3D program I used. Don't know if you have to do so on your 3D printer as well. To install this part to the N64, remove the top, then the original "region locked" cartridge slot, and replace it with this. Then screw the top back into the console.
As you can probably tell, this is a universal copy of the actual N64 cartridge slot. The dimensions may not be correct though, as I only had access to a ruler while making it. Thus, I am posting it as a work in progress. I used blender to make it. I simply added a plane, extruded it a couple of times, added a solidify modifier, and used the boolean modifier to make the screw parts and the holes.