I think clear shells will be as close as you'll find. I'm sure you can find ones that aren't sparkly, but with 30 seconds of searching these were the first ones I found that didn't have open face joycon shells:

https://www.amazon.com/dp/B09K43T1DN

I've not had problems with scratches under the shells, but I do take them off and wash them once in a while. (I run the tpu shell under water and I wipe off my controllers at the same time.) Because you can get grime under the shell.