You could always have towerbiminis.com (Barrio Upholstery) build you one. They may even be able to use the OE MC mounts on the tower.
FWIW they do excellent work. Had one built for my PS 190 and the quality was every bit as good as the OE MC ones.
I paid about $750 IIRC for one with a fancy 2 tone canvas several years ago. Guseeing you could get a custom one from them for about the price of a MC one, $1000 +/-.
'06 X2 MCX
"I understand why some people may not want to do this the way I have recommended but I can't understand the death grip some people have on a toilet plunger with a hose fitting." -JimN