marine grade bottle snap for about 15$ each
That seems a bit expensive, unless they're crazy good. Check Dive Gear Express. I spend about $5.5 USD on
my giant 4 or 5 inch bolt-snaps, and less $ on the smaller ones. Though I usually buy bulk packs of smaller bolt-snaps, just because I use so many of them.
If you want to spend a little more than $5, Piranha has some
Easy Grip Swivel boltsnaps, that are great for cold-water diving, gloves, or difficult-to-reach bolt-snaps. I use a few on my SideMount butt-pouch.
The other thing that can be useful, is tubular webbing, to go around the hose-clamp to reduce scratches on the tank. You can get it on
Amazon, ebay, or DiveGearExpress as well. I think 1-inch tubular webbing is the right size.
My tank-bands were made from bungie, although that does have a tendency to "roll" a little. I have experimented with elastic, but didn't have better results. The ones you get with commercial solutions are probably slightly better. You don't have to use the elastic band, but it can be useful if you sling the tank (front or side mount) for retaining the hose.