As Banzai has stated above, you're simplist solutiuon is a bag with straps. But if you want a nice bag, then I will throw my vote with the others for Acorn's bags. I have the small bag and it can hold all you mention above and be used with panniers and camping gear. It can also be relocated to your handlebars should space become an issue. I have actually lashed stuff to the outside of the bag, so it is very flexible. The leather straps should work very well with your B-17s loops.

I also have the Barley and it is a nice bag, but may be too big for what you have described above. It also seems like those things are harder to get as they always seem to be out of stock.

http://www.acornbags.com/smbag.html