Definitely worth looking around. I had a chat with a local stonemason and he let me have a rummage in his scrap skip. I ended up with a couple of offcuts from kitchen worktops (about 1" thick, not sure what the stone is but it is "real" stone not chips in acrylic).
He let me have them for nothing, I think that he was amused by my intended use!
I gave one of his workers a tenner to cut them to match in size, drilled holes for spikes in the base (long enough to pierce carpet and underfelt) and araldited them in. Big improvement in stability of my speakers and cleared up the base end.
LP12, Ittok (black), DV10X5, NVA Phono 2 (twin supply), NVAP50, Art Audio Quintet 15w power amp, NVA LS5 cable, Rega Ela mk1's.
Sony CDP XB930.