Wanting to know where to get heat abortion plate for steam deck.

Ok so I'm wanting to build my own custome steam deck but I've notice that everywhere I have searched there is one part you cannot get and was wondering why. Is it because is has no code or what? Ok so the part I am locking for is the heat absorbing plate plate for the inside of the steam deck. If you have ever taken one apart you know what I'm talking about, but that specific plate is nowhere to be found in the market I've searched high and low but with no luck so if you know where to get one please inform me.