Do you mean you can purchase a slab like a countertop material? or you would pour it yourself into a like a barrier dam integrated to your bench table?
Either/or concrete would seem an interesting option being both solid & vibration dampening. I know little about drilling holes like for your mounting lug holes.
Funny I was just thinking about the same thing for a different purpose. Make up some steel strips from C-section with threaded holes/nuts that matched the mounting lug pattern on a bench machine, then basically cast it in place with cement. I've read about guys using epoxy/aggregate mixture (as opposed to water type regular cement) on home brew CNC frames & they report excellent stability.