Yea that would be nice though since they would be technically be recreating part of trademarked product without permission then it could get them into a lot of trouble. Though noone ever really gets caught for it so it might as well be legal.
I'm not sure about the specifics but there are 3rd party cover plate sellers on Amazon Japan... I feel like if it wasn't allowed they wouldn't be able to sell on a site like Amazon. Either that or Nintendo has given them permission to do so.