I think acrylic is wrong selection because it is very easy to scratch it , it will lose its surface smoothness with time and it is harder to obtain with desired sizes. And there are acrylic photograph frame glasses and they are very successful to block uv.

And what is the abbe number of acrylic and glass for uv ? I think acrylic could lose its flatness and would deform in time. Thick acrylic would be very expensive for you. Nobody cuts its full size acrylic for you. You can cast your glass with liquid acrylic and hardener but if your polymer is not fresh , surface would be covered with colored diffractions.

Glass is cheap, its easy to order a desired size , higher abbe and index number and you can clean it with your wet wipe. Acrylic would be sensitive to chemicals and you cant be sure whats inside in your cleaner.

Plastic flat panels are sweet for applications but obtaining them in small sizes are very hard because they are for industry.