Mine is about 5 years old, brand is TIWKICH paid $50 delivered from ebay, came with a nice case, charger and various connectors, have used it to jump start other folks stuff a couple times and it worked exactly like it was supposed to. My only complaint would be it seems like it would be pretty difficult to connect to the tiny battery terminals on a Super Tenere.
just now plugged it into the charger, had charged it a few months ago and today it still shows 100% charged.
Very valid concern.
I've carried a Antigravity XP-3 for 7 years. Never had to use it on my Tenere until about a year ago when I was on a road trip. I had stopped at a park and left the key on, came back and would not start. Connecting the jump start battery to get a good connection was very frustrating.
The posts on the battery are recessed and the jump starter clamps were very difficult to get a solid grip on the posts.
The first thing I did when I got home was to order the pigtail that has the ring terminals on one end so you can connect directly to your battery and the other end plugs into the port on the jump start battery. I tuck the pigtail in behind the cowling and it rests at the bottom edge.
So now if I need it, there's no need to remove the cowling, just pull the pigtail out and plug it into the jump start battery.
So the moral of the story is whatever jump start battery you get, try hooking it up to your bike at home first.