Chosen Solution
So I bought a pre owned ps4 slim and it’s in decent condition but the glossy plastic between the two housing shells is scratched pretty bad. So I was wondering if that piece alone is replaceable?
If it’s the glossy black plastic, I think it is part of the entire top/bottom shell. Those can be replaced but you’d have to buy the whole shell. eBay is usually a good source for that. Sometimes you can find people selling them by themselves.