Jumping the gun a bit here, but, if these sell very fast, and you run out of SRAM chips, Mouser has this chip (263 in stock):
http://www.mouser.com/ProductDetail/Alliance-Memory/AS6C1616-55TIN/?qs=sGAEpiMZZMt9mBA6nIyysDfDw0vDQxSw%2fJdd2EqgHt0%3d
It would be about $7 each if you bought 100 of them, but they have the same pinout as the TC55BVM416, are TTL compatible and are in the same package. Probably bump the cost of the card up from $75 to $100, but at least you'd be able to make more of them using the same PCB.
The only issue I see is that the AS6C1616 does not support X8 mode. Only 1M X 16. I'm still not clear on whether you're using the TC55BVM416 in 1M X 16 mode or in pairs as 2M X 8.
http://www.mouser.com/ProductDetail/Alliance-Memory/AS6C1616-55TIN/?qs=sGAEpiMZZMt9mBA6nIyysDfDw0vDQxSw%2fJdd2EqgHt0%3d
It would be about $7 each if you bought 100 of them, but they have the same pinout as the TC55BVM416, are TTL compatible and are in the same package. Probably bump the cost of the card up from $75 to $100, but at least you'd be able to make more of them using the same PCB.
The only issue I see is that the AS6C1616 does not support X8 mode. Only 1M X 16. I'm still not clear on whether you're using the TC55BVM416 in 1M X 16 mode or in pairs as 2M X 8.