It is an interesting idea! With plastic? Plastic usually is not god for grip. Most shifter covers are made with over-molding, a rough plastic or rubber over rigid plastic. Can you post some more info? Thanks.
Here is what is out there for inspiration from AJT. I’m only calling them out because they already told me they aren’t interested in making these for 100 series LC.
They also have models with buttons on the side but these give the general idea. I think for ours the design would be more of a 2 piece front and back that screwed together at the middle seam.