The number you cited is an old Accutronics part number. If you meant that you went to amp parts suppliers and couldn't find the tank, that's probably typical, as this tank had solid-state drive and recovery circuitry, and most buyers are looking to do a tube-driven circuit.
You used to be able to order from Accutronics, or they'd direct you to a distributor for a low-quantity order. I'd suggest visiting their website
, and checking out the Ordering page. Worst case, you get referred to a distributor who actually stocks that tank. Or, they may make the tank for you to purchase (they used to do this via ebay for single-quantity orders).