GTX 680M thermal pads dimensions

I have an Alienware M17x R4 with the Nvidia GTX 675m and the appropriate heatsink, and i want to upgrade to the GTX 680m/780m but i have just one hitch in the process.

I'm on a budget, and the good thermal pads are expensive, on top of that i do not know the required thicknesses or other dimensions (lengths and widths) i need to apply on the GPU to ensure proper contact for all its components.

Can anyone provide me with a picture of the location and dimensions where thermal pads are...

GTX 680M thermal pads dimensions

GTX 680M thermal pads dimensions