Something you could attempt.
Get some PVC cement.
Coat the screw with oil or some other non stick coating, and dip it into the cement.
Carefully screw it into the stripped hole (just the screw! Not the part it holds on!)
The PVC cement reacts with plastic, and chemically melts it for a few moments, and then rehardens. With 2 plastic pieces, it will melt them into each other like a weld. With the metal screw, it should harden around the threads and form new threads.
JUST DON'T LET THE CEMENT DRIP ON THE VISIBLE PARTS OF THE PANELS OR ANY WIRES!
Let it set for a couple hours, and then SLOWLY unscrew the screw. As long as it doesn't crack, it should leave brand new threads to screw into.
DISCLAIMER!!!!!!
I have never tried this trick with the plastic on our scooters!
I've used it to repair parts on my nephew's electric ride on toys, and it worked great.
But, the plastic on our scooters is not quite the same, so NO PROMISES!
Maybe worth a try before buying all new body panels.