Not sure on the heat tape, but you could get some CHEs and buy large "clamp lamps" from home depot or lowes.. Use dimmer switches from walmart and put the snakes in tubs. Setup the clamp lamps so that they are above one end of the tubs and use the dimmer switches to regulate the temperature on the warm end...It wouldn't be ideal, and you'd have to adjust the temps often as the room temps change, but it would be something.

I keep a long strip of ultratherm heat pad (it is a very thin under tank heating pad sold by reptile basics, the one I have is about 8" wide x 36" long) I use this for quarantine setups and it could also be used to sit multiple tubs on during a case like yours.

Other than that, shipping heat pads will work also if you can get them.

I believe Reptile basics sells wired heat tape that could be used to replace what is in your rack, but not sure on cost, etc.