Up for sale are some buoyancy blocks of various sizes, all 34lbs per cubic foot. Rated to 4500psi with 2x crush rating at 9000psi. They have dings and chips here and there. Rough cutting to your dimensions might be possible. Price is $25/lb as is, or we can sort out a price for custom cuts. For reference, the taller pieces on the right are about 23"x23"x3" and weigh about 33lbs. Also have a bunch of small jagged pieces I’d let go for $8/lb and you could epoxy some together and then cut into more normal shapes. You cover actual shipping costs. Might be willing to trade for BR goods, or other neat stuff. Located in Northern California. Pretty sure this is Itar regulated, so no international shipping.