Temporary housing:
3 tubs with latching lids, either Sterilite latchbox or Hefty, widely available at WalMart, Target, Lowes, Home Depot, etc. Something like this:
https://www.lowes.com/pd/Hefty-34-Qu...ng-Lid/3341162
1 lamp dimmer until you can have a thermostat shipped:
https://www.lowes.com/pd/Lutron-Cred...Dimmer/4462373
3 heating pads (1 per tub, the 16W is a good size):
http://www.petsmart.com/reptile/supp...ml?cgid=500011
1 thermostat, it can run all 3 heat pads if they are the same brand and wattage:
https://www.amazon.com/Zilla-Reptile...2719491&sr=1-2
You may think that 3 heat pads + a thermostat is pricey but heat lamp bulbs don't last very long and in a year you will spend more than that on replacements. In addition those lamp bulbs pull a lot more electricity - usually 100W - versus 16W for a heat mat. Since they run constantly it adds up fast.
Then sell the 75-gal tank, you will way overspend trying to turn it into an appropriate ball python environment.