Puch Snowflake disc brake do it yourself.
Start with GM 12557819
It is an idler pulley off some car.
Center it up with the rotor, drill holes.
Cut out the center to match rotor.
Bolt together. Insert in hub. It will not just insert, you need to pound it in. It's a nice tight fit. I got it all the way in until it bottomed out.
Now put the wheel back on the forks. You will need to spin it to make sure it spins true. Theoretically, if the rotor assembly bottoms out on the inner hub, it should be straight. Mine was perfect. Make any adjustments needed before moving on.
Fit the caliper on the disc to where you want it to sit. Pull the brake lever to lock the pads in place. Rubber band out tape the lever closed. You can then make a steel bracket to weld to the forks. Line everything up tack in place. Check to see wheel spins and brake works. If all is good, weld that shit like a boss.
Ill get a few more pics once I mount the forks to the moped.(edited)