I'm just finishing up a custom motorcycle project; a cafe racer. I'm excited to photograph my bike in unique settings. I'm looking for a good padded backpack to hold a few cameras (XD11 & DSLR) that to isn't to bulky that I wish I didn't have it with me. The other issue I've had with backpacks and motorcycles is that with a leather riding jacket, I have a very hard time getting the correct arm-swing to get a packpack into position.
Are there any motorcyclists here that can recommend a good packpack?
This may not be what you are thinking of but have you thought of a 'tank bag' and you make your own custom foam inserts.
For what it is worth I am the big fan of classical tank bags, may be more of a continental or European thing but it works. Look for the tank bag that converts into the backpack? Second suggestion may be the large messenger bag, over one shoulder.
May I suggest Aerostitch as a source?
I use a LowePro Slingshot 200AW when riding. Carries a body2-3 lenses,flash,film and other sundries comfortably. Think I paid $70 US for it. Been updated since I got mine.My daily ride is an Aprilia Tuono if that helps.
The Crumpler Karachi Outpost, looks great and has a double front lock that will prevent the camera to move or be some kind of "parachute", it also have some kind of "vintage" look that will match your bike!