The closest replacement for your Forest River Roo fresh water tank measuring 28" wide x 6" deep x 54" long is a 39-gallon fresh water tank with dimensions 54" x 28" x 5.75". This tank is slightly shallower by 0.25" but fits most installations well. You have two options: 1) Purchase the tank with up to five custom fittings professionally spin welded onto it. This installation service costs $208.33 and ensures fittings are securely attached. 2) Purchase the tank along with all the fittings and a tube of sealer separately, allowing you to install the fittings yourself. The tank alone is priced at $245.00. Delivery times depend on current stock and shipping method but typically are processed promptly. You can view and order the tank here: https://elkhartrvparts.com/products/rv-tanksrv-fresh-wat. For fittings or installation accessories or to arrange custom fitting installation, please contact Elkhart RV Parts customer service.