Deck has not yet found a suitable adapter. Be careful with USB to PS/2 adapters! I believe that most (if not all) of these adapters were meant to be replacement adapters for original equipment; they will not simply convert any generic USB keyboard into a generic PS/2 keyboard.
To date, we've evaluated two adapters. The first was Cyberguys item # 131 0845; the second was xPCgear item # CBKMXPUSBPS2. Neither of these two adapters will work - do not purchase them! They simply map "USB D-" to "PS/2 Data" and "USB D+" to "PS/2 Clock" (as well as +5V to +5V and gnd to gnd).