You have a couple options if I am reading your post correctly.
Option 1
If the thermostat works fine you can simply drill a 1/2 hole next to the existing switch and use a 15 amp toggle switch like this one
Just connect the 2 wires from the old switch to the new switch and your good to go
Option 2
Connect the two wires on the existing switch together, bypassing the switch completely.
Plug your pot into a multi-outlet power strip and use the switch on the strip to turn it on and off
Option 3
Connect the two wires on existing switch together, bypassing switch.
connect the 2 wires on the thermostat together, bypassing the thermostat.
Build or buy a PID. Don't look back.
I personally would go with option 3 as your quality of your boolits will go up as you will be running a more stable temp because of the PID setup.