I’ve seen a craigslist ad for a longboard with some sort of cane attached to the front trucks. it wasn’t a steering wheel, but looks like a cane with a bit of a grip attached to it. I can’t find it on google. It looks much more compact than an actual scooter handle.
Look up K2 Kickboard. I used to have one and loved the way it turned. Somewhat like a skateboard by leaning. It has a handle that is straight with a ball on top. It had a lot of control. Someone needs to make an adapter that can be mounted above the truck on the deck, my wife would find that useful. Just screw the handle off when not used