M-Audio MIDIsport 4x4 USB MIDI Interface 4x4 In/Out Studio Controller - used

Tascam US-4x4 4I/4O USB Audio/Midi Interface With 2 Headphone Jacks

M-Audio Midiman MIDI Sport 4X4 Anniversary Edition 4-in/4-out MIDI interface

MIDI Solutions QUADRA THRU 4-output Active MIDI Thru Box

Vintage Roland MM-4 MIDI Thru Box Interface Japan No Power Cord

Vintage Roland MM-4 MIDI Thru Box Interface Japan

MIDI Solutions MultiVoltage Quadra Thru 1-in 4-out MIDI Through Box

lots of midi accessories: roland midi cable, usb to midi and Midi solutions thru