Is there a 0.5mm thick thermal pad? If there is none, will there be any negative impact if I use double or triple layers of 0.13mm?

Will using thermal paste enhanced the effectiveness?

Is it possible to have the dimension 15mm x 15mm?

Please also pm me the price. My ideal size would be 15mm x 15mm x 0.5mm. If not available, you can propose me something close.