Not sure if they have anything like Soilmaster, Schultz Aquatic soil, or Turface (most commonly used on sports fields) in the UK but try checking a landscape and garden shop for a fired clay substrate possibly for pond use. They're usually much cheaper than specialty splant substrates like Fluorite or Eco-Complete, 10-20$ for a 50lb bag. There may be cheaper alternatives like laterite or vermiculite but these are easier to use, just like regular gravel.
Layering sand over another substrate don't last long, the sand will eventually sink under any larger grain substrate.