Since my PegII is winging it's way around the world, I can't check, but the G3 modules definitely have the mounting clip holes for a standard VGA cooler.

If the G4 module has these (99% certain, see http://www.morphos-news.de/temp/peg2/pegasos2_g4.jpg) then you can just go out and buy a kick-ass GPU cooler.

The ThermalTake Orb series fits perfectly, and the fan on it is quite powerful (
http://www.thermaltake.com/coolers/chipset/menu.htm)