If $$$ are a concern (believe me I know from experience) this is what I would do. Leave the defective switch in place, but remove the wires first. Go to Pep Boys or your favorite auto parts store and ask them to sell you a simple toggle switch , rated at least 10 amps. This should be less than $10. You will then mount this new switch under the dash, in an inconspicuous place, and re-connect the wires. This way, no one will ever know that the old switch is defective and it all looks original. When you need heat, just reach under the dash and flip the new switch.
Note: you will not have speed control of the blower motor. The old switch incorporats a rheostat that provided a crude way to vary speed. You will have either no fan or 100% fan.
Good luck