Some great advise here and plenty of research to be done. Thanks to all.

I found this tail bag that I really like
http://www.cyclegear.com/spgm.cfm?L1=2&L2=55&L3=&L4=&item=FTL_CAR022
The picture does not show it that well, but the curve of the bag matches the curve of the seat/fender. I have managed to strap it down so that it does not touch any of the paint or chrome.