From what I know the motorcycle bag refers to all the bags that have the motorcycle fact. Therefore, the city (medium size bag that you want), the first, the weekender, etc. are all motor bags. (I think) I actaully wondered the same thing when I fisrt became interested in these bags
And I would check aloharag. I know they have some colors in stock -- or at least they did when I checked last week I think.
I would try Balenciaga New York. They are currently getting the new spring 2006 bags in, and I think they still have a pretty good selection of pre-Spring 2006 bags available too. Their phone number is: (212) 206-0872.
Also check out the ateliernaff blog that is linked above. You will find information on styles and colors there.