Originated From AOL Search
Try NP-1. It's a little hard to find but it's out there. I use it for everything. It can be found at industrial supply outlets, not Home Depot or Lowes.
Ask at a tile store. They may have a plastic compound you can add to grout. Just a guess.
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them