I hadn't read your post properly this morning, and I didn't get you are actually looking to BUY a pedal box, and not do it yourself.
Sorry about that
I checked OBP, but their narrow "kit car" model is 241mm wide, so too wide for the MT75 chassis, which, according to the MT75 chassis drawings, should be 214mm wide max.
http://www.haynes.co.uk/forums/showthread.php?t=2430
Sorry I can't help abut where to buy a fabricated pedal box that will fit a MT75 chassis, but I'm sure someone will come with a tip or an idea.
Good luck
