It is not generic. I bought mine from usedhandhelds.com but they are out of stock now. do a search on that site to get the number. Should be easy to find though. I'm glad you like the 790!
And if all else fails, you can still get them from NEC. The 790 is not an "end-of-life" product yet (the 780 is), so accessories are still available from the OEM.
