GeekyBob

While they may be difficult to find, the Furman SPB-8 case works great for the Line 6 M-13. I have my M-13 mounted to the board with Velcro, and I have enough room on the board for both a wah pedal and volume pedal. I will admit that it's larger than what you were originally thinking, but it's fantastic for hauling the M-13 around with other gear.