This thing is super easy to make and works really well. it just requires about 5-10 minutes of soldering. So here it begins:
I decided to buy one of these super crappy g-tron sega saturn usb controllers.
It worked fine at first but the d-pad is so poorly made that it just snapped after 2 days of use. I tried fixing it but it didn't work out. Then i realized that the g-tron controller's case is so similar to the official saturn controller's case. i took it apart and swapped the motherboards and it fit fairly well. The only issue was that the shoulder buttons on the g-tron controller didn't fit correctly so i desoldered them and replaced them with the official controller's buttons.
This is what it should look like at the end:
Thats all there is to it. It is so incredibly simple and it works really well.