Here's an old bag that you can mount on your tank...
Larry and I have been friends for 28 plus years.Thats just the way we are.
I use this one and like it pretty well. http://www.sporttour.com/luggage/cortech/tank_bag_super_mini.htmI put it on upside down from the picture, right where the tank meets the seat. It's stable, high winds don't effect it, has a map window, pretty organized interior section, too. As for messing with the speedo, nothing squirrely so far.
VTXGRL thanks for the info went down and bought one today and as Blueflame said works great at better than highway speeeds lol.Its a perfect fit not to big and not to small just right