Do you have a separate room for your snakes? If so, simply try partially closing the vent registers and keep the door closed. I have a dedicated snake room, but don't have separate heat/AC and it has worked very well for me. I check on my snakes multiple times a day and if it gets a tad warm or I know the forecast is calling for warmer temps, I'll crack it open a bit more. Has worked for me perfectly.
If you don't, CHE or a bulb on an adjustable pole and a dimmer and cover 2/3 of the top with wet towels or foil. Use the temp gun to make sure surfaces inside don't get too hot.
As far as the fire hazard, bulbs are more of a fire hazard than UTH. I use Flexwatt on Herpstats and the enclosures sit directly on top of low wood entertainment centers and are stacked on top of each other (PVC AP enclosures). I have my High/Low alarms set to +/- 5 degrees and if it hits that, the Herpstat shuts off the Flexwatt. Another advantage of investing in a good thermostat. Fires are very rare, but can happen with ANY electrical appliance.