I don't think there is such a thing. The vapor barrier is the 6+ mil plastic that gos down prior to the slab being poured. If there is no vapor barrier, the slab will wick up moisture from the ground. (Think of concrete as a very dense sponge) As far as I know, nothing, no coating will stop it.
As far as the comments that nothing will hold up, I disagree, As long as the vapor barrier is in place. I have seen slabs with epoxy coatings that have lasted many many years, and still shine like a waxed floor.
There are no band aids. It has to be done right from the start.
