Although I'm no sissy, I do want one. I have fond memories from my youth (I was about 27 at the time) of my first big bike, a new 1972 Honda 750, on which I installed a rather tall sissy bar. I rarely rode two up, but I really enjoyed that sissy bar myself. I'd put the bike on its center stand, then sit back on the seat against the sissy bar with my legs up on the tank. It was so relaxing and fun. I spent lots of time that way just watching the world go by. It was like having my own portable lounge chair where ever I went.
But, I don't want to encumber my scooter with a permanently attached sissy bar. Nor do I want a top trunk. I'm thinking about an easily removable temporary sissy bar that simply slides down over the upright part of the stock Vespa rear rack on my GTV 300. I measured it, and if I make it right, when off the rack it could be stowed by attaching it to the underside of the seat. It would be completely out of the way there.
I don't want to reinvent the wheel here. So if any of you know of an existing sissy bar similar to what I've described, please let me know. And, if any of you have suggestions as to how it could be made, I'd like to hear that too.