For heat alone (daytime UVB lighting is of paramount importance), I would recommend a ceramic heat emitter. This way you can provide heat at night as well without light.
These CHEs also require a special hood, as the CHEs get hot. So you need a hood/fixture capable of handling such. An shop light hood with a plastic bulb receptacle is fine for a 60watt light bulb, but I wouldn't use one for a CHE. Fire hazard!
A hood like this is needed with a ceramic end for the CHE to screw into.
A CHE will easily last a year or more, so the extra expense isn't all that bad.
You need more than one thermometer in your enclosure. And want to shoot for daytime temps of 95ish and nighttime temps of low to mid 70s.
Hope this helps, ask if you have further questions!