Lexan? Cut with jigsaw carefully and sand the edges. Buy at Home Depot or Lowes.
Acrylic will fracture.

PETG.
Find sheets on ebay

Here is my template, if it helps.

gb_protector (resized).jpg

I cut a protector from a sheet of thin Lexan a few years ago as a fix in a MET (airballs from Sparky’s feet). I drew the template (more or less eyeballed) on the protective film, used Lexan scissors (NOT general purpose arts & crafts ones!) to cut, then clamped it between two scrap wood pieces to cleanly drill the mounting holes and minimize burrs and hairline cracks. I intended for this to be a quick and dirty quick fix while I figured out a more permanent solution, but the end result looked much better than I expected and has proven to be perfectly durable, so I never bothered to try to improve it.

Cutting out the template above would be super easy with this method!

(Lexan sheets and scissors are usually sold at hobby shops which stock R/C cars & planes. I recommend “Excel” or “Dubro” branded curved scissors.)