Another option is to purchase some 3mm thick UHMW sheeting and make a rear cab, use clear Lexan for window. If you’re handy it’s not that hard to do. I made my whole cab, when I bought mine in fall of ‘14 there were limited options for the P5 even through the dealership most stuff was back ordered. With basic hand tools for wood working UHMW is nice to work with, incrediably robust material. Over the years I bought a couple sheets usually 4’x10’ by 3mm thick and use it for a host of projects. It’s good stuff and stands the test of time and abuse.
Have pix in sig link for, roof, rear cab, front windshield (will be redesigned in V 2.0, I want it to tip out). Stix stoppers and skid plates all made in shade tree fashion in my yard with basic hand tools.
I’ve had fun doing it and cost wise, I’m gonna say significantly less (if you don’t factor your time), then buying premade.
Cheers,
j