When I had to replace the clear safety shields on my grinder, I just made new ones in the same size and shape from polycarbonate plastic. There are several kinds of clear plastic sheeting available and you do NOT want to use the cheaper variety sold for common window replacement. You do want polycarbonate and Lexan, made by GE, is one brand but there are others. This is the material, in appropriate thicknesses, that are used for things like security glass in banks and convenience stores and in railroad locomotive windows.
Your home improvement center should carry it but, if you can’t find it, most industrial plastics specialty stores will sell small pieces and give you some tips on fabrication. You can drill it OK but sawing it can be a challenge as it can melt back together. Scoring and snapping, like you do window glass but with a straight edge and something really sharp run over the line a half dozen times, is better than sawing in the thinner thicknesses.