http://simplyplumbing.com/amtrol-wx-...hannelid=FROOG $403 including shipping - 44 gallon tank
http://www.sprinklers4irrigation.com/en-us/dept_3356.html This seller says the Flex-con is exactly the same tank.
Also available at: http://www.pumpsandtanks.com/Tanks/ Call for shipping
You might want to negotiate a bit. Looks like about $600 for installation, which is one pipe connection unless there is significant replumbing.