Someone has, but it has been over 15 yrs since I have seen it. It was a back rest arm rest combo on a Shadow. My wife saw an umbrella on a GW at the fuel station and wanted me to get one. Oh hell no! Anything that is wanted can be found on eBay if not then I suggest you find a fabricator to make one.
I know I saw someone had made one, I think out of square tubing, which was a big U shape, and it could be pivoted up to stand straight up so passenger could easily get on, and then tilt it down around them. I think it might have been on the h-dforum, though. I haven't seen any manufactured and sold by any company, though. Maybe you should make one, and sell the design to one of those companies.
Need suggestions for replacing stock seat on 2019 electra glide standard.
Would like to find a 2 piece seat with removable passenger pad and a removable driver back rest
Or a one piece 2 up with backrest. Not finding much on internet for this bike