Helix or Herpstat for proportional thermostats. Johnson and Ranco for on/off type. Proportional will run continuously, but only supply enough power to maintain the desired temp. I would google search and look for the best pricing. I got my Helix thermostats from Reptilebasics.com and I love them. You could even try posting a wanted ad in the for sale/wanted section on this site. Maybe someone has one they are looking to sell.
alot of people go with the expensive one but a repti therm 500R works well for me. Temps are not constent BUT they range from 92-94. I like it and for $30 its nice
I have a Johnson controller on one of my racks and a 500R on another...both work ok. I will be replacing the 500R with something else soon though. Looking into the Big Apple brand t-stats.