We have 6 used Ranco ETC-111000 temperature controllers that we used to control the solenoid valves on the cooling water supply to our fermenters. They have a controller unit and a temperature probe connected by a ~7' of wire. These have adjustable set points and are pretty straightforward to wire. You can tell they've been used but they work perfectly fine - we stopped using them when we increased our number of fermenters and moved to a system with data logging.
Retail is $60. Will take $20 each or $100 for all of them - buyer pays shipping.