As you can't get a replace rewind knob for the AE-1 Program here in germany (or at least not under 40 bucks), I decided to print one myself.

This print is made to be paused half way to insert the original screw for the knob and resume after the screw is placed.
You can as well use another generic screw with the right thread and pitch, but you may need to adjust the clearence for the head then.
It'll be a standard metric M3 screw (0.5mm thread pitch) and it needs to stand out about 3.5mm from the bottom of the knob.

For the print you need to add some clearence to the buildplate (5mm is enough) and print it with supports under it (of course not at the hole in the middle) so the thread of the screw can hang free in the air.
Because some guys had issues with making the knob float in Prusa Slicer, I uploaded a second STL called "floating" with some pillars under the knob. You can still set your own supports, its just to make the floating easier.