Hey Ralph; Heck those bricks are lite... shipping would be cheap... if you could just talk the seller into shipping 2 dozen to you.
Really these things are out there all across the country. They are just in the industrial section. Normal folk just don't see them. Anyplace there is a boiler there are firebricks.
Start hanging out down at the guard shack of your local pulp mill or sawmill or refinery. Wait for a turnaround (temp shutdown) There will be refractory company vehicle's , those are the guys to talk to. I guarantee, if you could talk to the correct person they would happily sell you some insulated bricks, probably not for .50 each though...
I have even seen insulated split bricks ! Piles of pallets with heavy bricks of many sizes, pallets of full size insulating bricks, huge stacks of bagged refractory mix.... enough to make you starry eyed!