As far as I know, they're only available from
http://www.grassypavers.com
I checked Lowes, Home Depot, Ace, and my local building/landscaping supply.
I don't know how they'll react to a bunch of orders of 2 each.
If there's a lot of interest, maybe a homebrewer in Mississippi could get a
full pallet and break it up.
The hexagons are 2.125 inches.
2.5 inches would be better, and I'm sure someone in the world makes a honeycomb that size, but I have no idea how to find them.