I always carry a 3-pak. One time I needed it. She arrived and said she didn't have any. It was either a ploy to upcharge for bb, or a ploy to say no sex, and get the money anyway. I just pulled mine out.
It is the lady's responsibility.
Absent some over riding reason (allergies, size, etc.) the lady should provide them. If an over riding reason exists, he should inform her, or provide them himself, preferably the latter.
EDIT: A previous thread with a poll can be found here: http://www.eccie.net/showthread.php?t=19194