I searched for these when I was laying my track, with no success in the UK, and I ended up doing it the hard way, with shallow trench, membrane, edging, sand and ballast. In retrospect, I think I would rather have made a former and then cast my own blocks like these, as I ended up having to rip it up and redo it after only 3 or 4 years when the low quality membrane failed and then I bit the bullet and laid membrane of the quality I should have used in the first place! Most of my track elsewhere is laid on baseboards made of timber and marine ply, topped with thick roofing felt and sitting on blocks to keep it just off the earth, but that's even more effort to produce!