Where can I find a non-slip rubber/vinyl bathtub mat for reglazed tub?

I mean the kind for inside the tub (to keep babies from falling), not one for the floor. We had our tub refinished, and they told us we can't use a bathtub mat with suction cups. I found something with a stick-on back, but I really don't want to do that either - since it's just for 2 months (would rather have something removable). Any ideas?