I have the following tank bag for sale:
http://www.rideicon.com/gear/mens/ba...-bag/cityscape
It is pretty versatile and has back pack straps as well as a sling for carrying a helmet, which comes in handy if you are flying somewhere to ride. Doesn't not scratch the tank unless you get some grit under the magnets, and really needs a velcro strap, or something similar, to secure it to the handlebars for extra security. I will throw in the strap I used.
I used this bag once on a trip from FLA to MSP. It's in really good shape.
I paid $100 for it, and the first $50 or best offer gets it.
PM if you are interested.