JTEK Shiftmate is what you'll need I believe if you want to do this... Currently I'm running Rival (SRAM) 10-speed with my 9-speed Capreo (Shimano) cassette in the rear on the Bike Friday folder. Works great.

Edit: looks like model number 5 is what you'd need. Contact them directly via email if you have any questions. They were very helpful and responsive with my setup questions.