Seat top cargo bag

What is that bag in the forum picture? Is it large enough to hold a helmet?

It's mine and it will hold a ff helmet. Check motorcyclegear.com for "FirstGear Onyx Expandable Tail Bag".
It expands upwards another 2-3" and comes with a rain cover and shoulder strap.

I had to do a bit of kludging to get it to work. I cut up some memory foam and had my upholsterer friend make a "pillow" to level out the passenger seat. I tossed both bungees and used a Rokstrap on the rear. For the front I went to JoAnns fabric and got 2 sets of nylon quick release buckles and some nylon strap and threaded it through the part where the bungees went. I put a male and female buckle on each side of the grab rail and made a matching strap for the tailbag which, combined with the Rokstrap on the back, gives me a quick release with more peace of mind than using the bungees.

This sounds like a lot but only took me about 1/2 hour to do not counting the "pillow". I don't like the looks of hard trunks and this will hold enough for a 3-4 day trip. It seems very secure so far.

We found the bag as you had listed and it is not even a bad price. Love the look of the tail bag along with your back rest. The overall look doesn't shout scooter which is one reason we like the look.

I like the looks too and it works great as long as you are solo.

I just packed it for a 3 day trip to Idaho tomorrow and I'm impressed. It holds:
2 pr. shorts
1 T shirt
1 pr. sandals
2 pr. sox + 2 underwear
sm. toiletries bag
my mac book air + a small bag of misc electronics- mouse, chargers etc
the 2 small outside pockets hold my light weight leather gloves and my mesh gloves with room in the large pocket for my winter gloves
All of this without expanding the top. With the expansion I can fit my jacket and pants liner.

Under the seat is my rain gear, covers for seat and bag, cpap machine and a down pillow which I insist on having.

We both ride so no need to worry about a passenger.

Our next modification will be to add the backrest. So many options.