Do it right
Set the bike up with proper racks and Jandd panniers.
The used market is full of folding field cameras. Photobackpacker sells cases for cameras. Fishpond sells fly reel cases that hold 2-3 lenses.
There are lots of tiny lenses around. Fujinon-W 125mm and Kodak Ektar 203mm are two that come to mind. My Speed Graphic came with a very good, very small Kodak Ektar 127mm lens.
There are decent compact tripods around too. They may not extend way up high, but they will hold your camera steady.
A friend of mine has what may be the perfect sheet film bike camera: A folding 3 1/4"x4 1/4" Zeiss with a 150mm Tessar lens. Folded it's no bigger then my Pentax 6x7. It makes negatives a lot bigger than 6x7 or 6x9.