Airtech is now listing thier large dustbins on the web site. It's still only 20" wide but looks like it could be cut and widened as it approaches the riders legs. Just thought I'd post before you start cutting aluminum for the front.
Anyway search "Airtech dustbin" or go to
VINTAGE HALF FAIRINGS, CAFE, MANX, TRITON, DRESDA, TRIUMPH, NORTON, BSA, BMW, MOTO GUZZI, DUCATI, HONDA, SUZUKI, KAWASAKI, YAMAHA.
Seems like a good alternative to DIY for $595, plus mount fab, windshield, paint, etc.