I just found this thread. Very timely because I have been on a search for the same; creating my own plastic pickup covers.
Recently, I found one of these locally on FB Marketplace...
All it said was vacuum forming machine. I was immediately interested.
The model name was Pro-form, I looked it up and it is a small machine used in the dental industry. I felt pretty sure that this would work for what I needed.
Then, I looked up using this machine for hobby purposes. Adam Savage (who wrote one of my all time favorite books; "Every tool's a hammer") had posted another video about using one of these for other molding uses. THis sealed the deal.
It took me a couple of weeks to hook up with the guy. It was worth it though as he told me that he had two of these machines. Both worked, I bought them for $25 each. Score.
I found other similar used machines for around $100.
I decided to make a cover for a Gibson EB mudbucker, due to it being a simple design. I made a wooden form/plug. Note; I made it quickly, I wanted to play with this thing.
Adam's video helped so much. One thing I didn't listen to was keeping the plastic sheet away from the heat source, it was cold in my shop and the heating element took a bit to heat. Again, I got in a hurry and placed the plastic up against the heat element. I did it twice, with the results pretty much the same (i waited until the plastic was smoking. Not good.). On both pieces, the finish ended up somewhat rough. The first time I tried it, the plastic sheet came with a protective layer and I left it on. It never came off. Lol.
The second try looked much better, but still rough.
The .060" turned out not to be thick enough. I have ordered some .060" black ABS plastic. I feel that it will be thick enough and hopefully it will still be pliable enough.
I'm going to make a more accurate form, with little, if any roundover. I would like to look Fender-ish if that makes any sense. I feel like this can make a professional looking pickup cover.