Can anyone recommend a source of weather resistant clear window plastic

This is less backpacking and more bikepacking related. I’m sure you guys aren’t putting plastic windows on your MYOG tents like the ones on the canvas family tent we used when I was a kid, but I know there are some good materials guys on this forum. I have a front bag on my bicycle that I use pretty much daily. It’s an older version of this one. After maybe four years and 1000 hours of use (not all in daylight) the clear plastic over the map area is cracked in multiple places.

It looks tedious, but I don’t mind doing the work of replacing it as long as I don’t have to do it again in a few years. I’ve had reports from other cyclists of similar map pockets from other brands still being fine after 20 years of use, but of course the makers don’t say what material they’re using.

Suggestions? Some kind of polyurethane? It does need to take low temperatures without becoming brittle, as I ride year round, down to -22 °F (-30 C) so far.

Thanks!