I'm in the process of listing the various Shoggoth models on the market: https://alkony.enerla.net/tag/minispecies-shoggoth-cthulhu-mythos
Currently the only one fitting the description is the : Colossal Shoggoth from Fenris Games
But as that sculpt is not very exciting, for that price I'm almost sure you can create something from scratch - you can use polystyrene foam, sea sponge, or whatever you have at home.
