Ok, I just bought a mini LST with a brushless setup on eBay, it is a Hobbywing 35A-SL. I wasn't paying attention to the pics well enough to realize that the heatsink was missing. The ESC still starts and runs a motor well (I tested it with a 2S lipo to see if it turned on), but I don't want to run it without a heatsink in the truck. I work on Xbox 360s, and have a ton of heatsinks I can cut to size to fit on the ESC, but I don't know if it's safe to put any kind of metal or Arctic Silver compound on it. In the pic, I see that it has solder on the top but I don't know if it will conduct electricity and fry the ESC if I put anything on it that's metal. If it works, I'll throw all the info up for anyone else. Any input is greatly appreciated, I'm willing to try anything to make this thing run well and not fry!

I have no idea where you could get a heatsink for it.

I would assume that if you could find one then you could replace it, it may need thermal grease or something like that like a CPU heatsink uses... but this is only blind assumption.

Advice is to call the the manufacturer and see if they have a part, and also call the seller and see where that heatsink ended up and ask if you can get it sent to you.