For what it's worth.....two things that I bought for the agility that turned out well were a windshield and a modestly priced, lockable top box, with mounting frame.
The box sits rather like an egg on the very rear most part of the scooter frame and has at least, if not more space than the underseat compartment. It was sold as being adoptable to the agility, but I was not able afterward to completely lower the seat back so that a passenger could be seated....which in my case did not matter............Anyone wanting to pick up groceries or take a weekend trip would find that this set-up could handle as much as he might cary in his arms or on his back...adding in a net or a few bungie cords.....Good luck