Use "is" if you think there really is a way, but you just don't know how to do it. "Is" is not contrary to fact.
Use "were" if you think there really is NOT a way to do this, and you know it to be contrary to fact. This is the subjunctive.
Technically, you should not use "was" -- but you're going to hear that more and more as the subjunctive slowly disappears from American English.