I've created a simple wallet for 3D printing in OpenSCAD, this is the third iteration.
It's printed in one piece with the hinges already in place. The SCAD file is not super cleaned up, so be aware that everything is not super modular if you decide to change anything. You'll also need
The protrusions on the sides are made for 10 mm neodymium magnets. I just fastened them with a glue gun, but one of them fell out and I'm too lazy to fix it, but since I always just have it in my pocket it really isn't a big deal.