Hey bagger, I recently installed a TCV (Temperature Control Valve) on my propane smoker. The TCV is designed for turkey fryers but can be adapted to any propane cooking device. Basically it has a temperature sensor that is placed in the cooking chamber, and an adjustable valve that is installed between the regulator and the burner. The unit costs around $25 bucks. Temp range is zero to 450 degrees.
I ordered mine from www.turkey-fryers.com
for $24.95 + $6.80 shipping.
I have'nt smoked anything with it yet, but tested it with an empty smoker and seemed to work fine.
Post some pix of your smoker.