The Givi tunnel bag was made known to me by Twisted Throttle, in that they have a section where one inputs the type of bike and, lo, the items that will fit the Majesty pop up.
I did this when I bought my Givi windscreen and bookmarked that page. Imaging my surprise when I revisited it and saw the trunk bag !
These hump or trunk bags probably exist in Europe, but, as far as i know, this is the only one here in the US.
Previous to this, I was trying to fit a tank bag to this space on top of the gas tank cover, but few bags are small enough.
The Givi bag is narrow and tall, with a 21 l. capacity [!] A 6-pack of 20oz. water bottles would fit easily.
Two dog ears flap down, and are velcro'ed to the sides of the center hump. This should be secure in about anything. there's also a ridiculous belly strap that probable would not work.
It is worth noting that this is a universal scooter design, made to fit several makes. The top just starts to interfere with the Majesty locking glove box, but not too badly.
The workmanship is good, styling likewise. The price is steep @ $87, and several niceties, such as a map window and non-slip bottom are not present. The map window is especially missed, as the top of the bag is level with the rider's legs. I'll be looking for an add-on window, even if it means cutting off the center handle to give a flat surface. [ There are TWO handles on top, anyway...] A rain cover is included.
What with the omissions, this is still a mighty handy and useful bag for touring that fits [almost] perfectly into an unused space. Combined with a tailbag [soft, or hard] and there's a lot of room on this scoot...considering the 69l. under the seat!
Well here's my review of the Givi tunnel bag. I will cut to the chase:
if someone makes a custom bag for the Majesty I would buy it instead. I bought the Givi bag a few days before that thread started.
There is nothing wrong with the Givi - it is VERY high quality, it's just that it's "one size fits all" which means it fits nothing perfectly.
It's held on to the tunnel with velcro flaps. You have to tape velcro to the tunnel and the pieces Givi supplies WILL NOT lie flat on the Majesty's tunnel - I needed a lot of creative work with a razor knife, and ended up with a less than beautiful result - but at least the velcro sticks.
Also the tunnel bag is a little to big - it is "squished" when put on the Maj, and interferes with the glove compartments.
As noted, it has no map case. It has two side pockets with zippers and one really big central compartment but with no dividers or side pockets. Since it is now my briefcase for work I wish it had something to organize things in the central compartment.
As for plusses: again it is very high quality. Two handles plus a detachable shoulder strap. A rain cover that looks like it will work (haven't needed it yet).
It puts your luggage weight low and in the center of the scooter which is best for handling. It has a little reflective piping (wish it had more).
Zippers have big tags so you can open them with gloves. Two year warranty. BIG storage capacity. And it's grab and go (but that also means you MUST take it with you or someone else will grab it and go).
Bottom line - If I were you I would wait and see if the custom tunnel bag for the Majesty works out. If not, get the Givi.
I mounted a small luggage loop from www.aerostitch.com on the front top center of the tunnel. This is useful with a carabiner to clip an extra bag of groceries to for short trips.
With this loop, it is possible to put a cable thru the tunnel bag in at least two places, and lock it on the bike. With a little thought, and a few tiny locks  , ALL the zippers and bag will be locked when I get off the bike.
Combined with a motion sensor alarm, the system is fairly secure for trips into grocery stores, etc.