I got two tires at $28 each, $13 shipping, which is about the same price as regular tires from a retail store. You'll need to remove the tire from your rim in order to measure it....see following link
Bicycle Tires Guaranteed to Never Go Flat
then pick which type of tire you want.
I've now read they're difficult to install...it's a good thing I'm a mechanic with a plethora of tools available!!