This one: https://www.amazon.com/dp/B08ZS2J7YT?ref=ppx_pop_mob_ap_share
Looks amazing, seems well made.
I got these so that they could blend into the back seats.
BASENOR Tesla Model 3 Model Y... https://www.amazon.com/dp/B08ZS2J7YT?ref=ppx_pop_mob_ap_share
Still has the seat pocket and install was 5-10 min.
I found one that actually attaches to the back plastic. It's made out of "leather" and goes in to the creases. Also retains storage space. I'll see if I can find a link. It was on Amazon.
Edit: here you go: https://www.amazon.com/dp/B08ZS2J7YT/ref=cm_sw_r_apan_glt_i_BVVFT4DH4SKWD7HSDWTB?_encoding=UTF8&psc=1
Edit again..just realized you meant the actual seat where the car seat gets mounted to... I just used a generic protector that most have.
I got a set of Basenor seat backs that have pockets for roughly this purpose. Otherwise there's no storage.