Spa thermostat, need more sensitive control? We have a Spa 'n' a Box, great element for our needs....

We have a Spa 'n' a Box, great element for our needs. Only problem is the thermostat variety is huge--like, goes on at 100 and sour at 108. I'd like to replace it next to a more sensitive thermostat--any ideas please?
Portable Air-conditioning?
Answers:    sounds similar to the thermostat is sticking. If it is under warranty hold them send you a current one. If not original equipment is still best or you could check someone close to Granger. watch for temp. differential, some are adjustable

http://www.grainger.com/Grainger/wwg/pro...
How can I fix up the window contained...
Electronic, digital heat controls (ETC's or DTC's) are great and relatively inexpensive. Set up parameters include setpoint and differential so that you can adjust what warmth you want and how much you want to drift away from that temperature beforehand re-ergizing the heating circuit. Name brands include Ranco and Johnson Controls. These are available at any HVAC wholesale counter.