USB Midi interface / converter

Your best mate is Shuttle Mate:
• 6 HP/TE width, 33 mm (1 1/3") in depth (super slim & therefore shuttle friendly)
• Merge MIDI and USB-MIDI into one MIDI and USB MIDI flow
• Perfect mate for Shuttle Control to be able to connect two MIDI devices into Shuttle’s 'to host' input (for example, drum
machine or sequencer and midi controller).
• no bus-power required—device runs fully on power delivered from USB socket
• works also as a portable USB host for USB-MIDI only equipped controllers

http://www.endorphin.es/assets/endorphin.es_shuttle_mate_manual_1.0.pdf

• Module is passive
• 33 mm Depth

No info about availability.