Wolfman Rainier
I have a Wolfman tank bag that I use on my v85tt. I'm pretty sure it's the 'Rainier' model, so 20 litres give or take. I don't think it's a current model but thought it worth mentioning as it fits the shape and size of the top of the V85tt tank like it was made for it - and they do pop up occasionally secondhand.
It's a well thought out bit of kit in other ways too - got a handy carry strap, a decent sized map pocket with a seperate pocket underneath for other paperwork and there's several external pockets, including a good sized one nearest the rider. All zips ae heavy duty and the pulls are colour coded so you don't do that thing of opening it by unzipping the expanding section...
Only trouble is finding one - mine came from here about 18 months ago.