Ice chest, Igloo, Rubbermaid, Coleman...
Large enough for your fermenter. Fill with water, creating a stable bath.
freeze several water bottles, swap out as needed, floating in the "bath" to keep temps under control.
WallyWorld sells indoor/outdoor thermometers pretty cheap - they have weatherproof probes for the "outdoor" part - drop that into the bath and you'll have a good idea of the wort temps, as a water bath method is very efficient at removing heat from the fermenter.
Shoot for the low end of your yeast manufacturer's suggested range for that strain of yeast.
The first several days (Active Phase) will raise the temps inside the fermenter SIGNIFICANTLY if not kept under control. - like 5-10F easy. Some have reported even 15F. You don't really want those conditions if you can avoid them. Your beer will be much better for it.