you could stack some cement blocks (12"x12"x2") to the desired height, put a 1/2" layer of heavy carpet foam on top and bottom, and then put your monitors on that. cover the stack with cloth to neaten it up. the block will provide a stable base with low resonance and the compressed foam on the bottom will isolate the stand from the floor, and the top foam - monitor from the block. use spray or contact glue to stick the blocks together - enough so they won't slip easy. you could use just about any block to get the height and mass - its not critical unless you're an audiophile.