I found mine ferreting around one of the local Electronics Surplus Warehouses. The nice thing about it is the fact that it has a long shaft, instead of a short one that you must use a screwdriver to adjust. that way, it sticks out the front of the case and I put a knob on it. I'm constantly playing with it depending upon my cpu load. In all honesty, you can probably get by with a simple switch. That way, you can put a fixed value power resistor on one side and bypass it on the other side of the switch for those times when you need all the cooling you can get.