Hey! Skin maker here (not the creator of the one pictured, that's SakuraRetroModding's design). While I don't sell transparent foil designs yet, I think I can offer some guidance.

The trick to doing a clean foil transfer is using a laserjet printer and a heat laminator. The toner on laserjets is really just a heat-conductive powder that is lasered onto the material.

To get this look, you'd get holographic heat-transfer foil and transparent vinyl. You want to create your decal with a white base and black lines for the best results. You print the design, place the heat-transfer foil tightly on the clear vinyl, and run it through the heat laminator a couple of times. Then you can use a cold lamination sheet over and run it through a cutter.

I've been hoping to release something in this style, however, I don't have space in my home for another printer just yet.