I did this fan.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
It's the same one trail tech uses for their kits. I also ordered the temp sensor and temp controller from trail tech.
Here's a pic
I had to make a bracket to mount the controller. It might be easier to just buy a KTM kit and modify it to fit. But I guess if GasGas has a kit that would be the easiest route. I couldn't find anything a few years ago when I was looking at doing mine.