Put them (or your film) in a transparent, zip-lock-like, plastic bag. Hand it to a screener around the metal detector and say something like "high-speed film check."

I've had pretty good luck with such things, though I had one screener give me grief for having some 400 speed film in the bag (it was a mix of about 6 800+ and 2 400- rolls). They'll probably look at it real close and do an ETD-swab on it. I've had them take as much as 2 or 3 minutes on a bag of film, but they've never messed it up. If they make you take a picture, they're doing something wrong.

Remember that the effect of x-rays on film is cumulative. I think the rule of thumb is that more than about 4 trips through for 400 speed film may fog it; the number is much lower for 800 (something like 1 or 2, can't remember).