I'm working on our shower floor. Some of the grout needs to be replaced. The tile is small hexagons, maybe a half-inch square each. Three of them popped off when I was scraping the grout from around them. I've cleaned out the area and the tiles.

I don't have any thinset. I'd rather not get a bag for what is essentially a tablespoon of thinset. All the premixed stuff says not to use for shower floors. Is there potentially something else I can use like some sort of epoxy? Or do I need to just get a bag of thinset that 95% wont be used?