Thinkpads with a dedicated GPU come with a dual heat pipe heatsink, whereas ones without the dedicated GPU don't. So, you can take the heatsink for the former and use it on the latter, given that you make sure to insulate the part of the heatsink that is supposed to cool the GPU (this can easily be done by using a quality electrical tape like super 88 on the bottom side). You can buy the part aftermarket or see if Lenovo is willing to replace yours. The part number for the heatsink I put on my T490 is 01YU186.