Photodon (https://www.photodon.com/) creates screen protectors for many devices - and this includes many pen displays. They have a choice of materials and you can even order custom sizes.
Direct link to their protectors for drawing tablets: https://www.photodon.com/screen-protectors/drawing-tablets.html
Installation process: https://www.youtube.com/watch?v=xnykx7BvKC4
Photodon has different types of film. Some have more anti-glare effect and some have less.
Of the films they have, the one that reduced glare but didn't add too much AG sparkle was the Photodon MXT AG film. Photodon ranks this as a "50%" reduction in glare.
Photodon has many pre-cut films that apply to a large number of drawing tablets. But they also offer custom sizes. You just need to know the size dimensions of the film you want.
Instead of guessing which one will work for you, order Photodon's sample kits so you can try out a little piece of the screen protection before you decide to purchase the full sheet.
These sample packs are inexpensive and i HIGHLY SUGGEST you try them out before you make a pruchase decision for a full sheet.
I tested out a sample pack of Photodon films in June of 2023. You can see my experiments here: https://youtu.be/3x5pfmbsQys