The ATLAS 550 Dual Nx 56/64 module is still in production. It is possible he looked up the wrong Part Number. The old PN was 1200311L1 which has been discontinued, but the new PN is 1200311E1. Hopefully this the only reason your reseller indicated it was discontinued. Ask him to order the E1 part number and you should be good.
Thanks Patrick. They fixed the issue after I assured them that the card is still in production