I can't help with the heliamphora right now, but I have a lot of really great silica sand I use in nearly all of my soil mixes.
I usually get it from Home Depot or Lowes. Over by the section where they sell the Portland cement you will find 50 pound bags of pure silica sand. It comes in a few different grain sizes, but I've found the course (aka 30 grit) size works the best. And it usually costs 7 to 10 dollars for the 50 pound bag. If you still have trouble getting some I can send you a bag full of it for free. Just pay for shipping.
They also carry peat moss but it's usually a bit expensive, but the bag will last quite awhile.
Good luck in your heliamphora search!
