Many years ago (sounds like a story lol) back in the 80's (I think) a local dealer was selling an auto scooter that I believe may have been a Benelli or Aprilia or similar. The main thing about it was the storage. It had a flap at the rear, a bit like a small bootlid, that you could flip open and this allowed extra long items to be slid in like fishing rods, or baguettes lol They could go right through into the leg area behind the legshields. The seat also lifted in the normal way. Probably anyone under 40 won't remember or know and no I'm not talking about a Piaggio Hexagon or Honda CN250. It wasn't a proper boot just a small flap. The dealer was Glanfield Baldet in Northampton and the original owner was Andre Baldet who was well known in the Fifties for his exploits on Vespas and special editions he created. Probably they sold better in Europe than over here as I don't recall seeing one on the street.
?,have you checked out Peugeot maybe. More current,but had a Vivacity that had a thing going on with a feature where you could slide a snake lock up it's rear end.
Peugeot Speedfights used to have that but it was dropped on later models. Don't think it was Peugeot that I was thinking pf. Pretty sure it was Italian.
Have you had a gander at any classic scooter spares suppliers/breakers.? you never know - something might catch your eye & give you a lead.