I have 2 that I use regularly. A very old magnetic Held one from the days when all bikes had steel tanks . I use that on my superlight but have to be careful not to scratch the paint on the tank. I also have a zip on one for a Moto Guzzi that came with the bike.
I had the DP one, which was great. It is quite tall too so helped as a wind breaker on the motorway too. Sold mine in the end but i have seen them on eBay.
Kriega bra works well to - you can use various size bags Kriega US Tank | Kriega Luggage | Infinity Motorcycles