Dear cedar, Indeed, dental dams are hard to find. But you can check places like your local health department's HIV clinic, which may either distribute dams or know of a source for them. With scissors, carefully snip off the elastic band part and tip of the condom and then cut down its length. If you're in a pinch, you can use nonmicrowaveable plastic wrap. Also, condoms were designed with sex in mind, while dams were created to help dentists focus on a particular part of the mouth during an oral procedure.
Condoms are less expensive than dams, and that also means a lot in the marketplace.