If you don't get a timely response from MMC, you could always try Safety Devices in Mildenhall, makers of roll cages and the like and see if they could knock up a new one for you.
Taking this idea further , I wonder if they could knock up a new chassis ?
Conceptually the three wheeler chassis is a fancy roll cage with body panels riveted on , and some accurately placed mounting points.
Probably not as strong as a roll cage , but thats another story.
I know I am simplifying somewhat , but ....
