I would take him to the vet. F10SC isn't available in the US right now (thank you EPA) so if you want any you'll have to buy it and have it shipped from overseas - $$$.
If you can't afford a t-stat right now at least get a lamp dimmer at Lowes or Home Depot, they're about $15, so you can dial back that pad before your snake burns itself and needs a vet visit for that too (and that's not a cheap visit).
There are a ton of decent but not too pricey thermostats available, including the VE Hobbystat and Hydrofarm. As with anything else though, you get what you pay for.