I have one that will fit. Brand new I had it made a few years ago for GS 1150. Didn't use it. Breathable soft inside so no scratch risk. You can have it £35 posted.
I know it's a bit big and ugly, but I'm genuinely impressed with mine......I spent three hours working on wiring in some relays and lights to the GSA last week, in the pissing down rain, in the dark.
I just partially closed the cover over and sat on a stool next to the front end with a worklight on.....stayed completely dry and warm as well, whereas with a conventional cover, It would have been impossible