If you really need a screen protector, just get some scotch or packing tape and put them across the screen. In 23 years of using DMM, its rare to really scratch the meter face to something horrible.
I only used screen protectors on the writing surface on my Palm PDA [ which tended to get badly scratched from the stylus] it wasn't a reading surface but the scotch tape worked well, just gummy to remove and needs cleaning when it wears out.