Well this is an interesting one. First thing first, Lenovo sucks for replacement unique parts like the back plate of a yoga. I also have never seen a shop offer the option to fix dents in laptop bodies either. So unless you can find someone to go around with a real tiny rounded tool, I doubt it can be "fixed" but instead replaced. And with some searching around, I can't find any source for back panels for a yoga. So your only real option left would be to buy a dead yoga that you can use for spare parts, and that will be hard to find. So if you can find someone to buy a back panel off of, thats pretty much your only real bet.