Ask at a lab that processes 8x10" film. They often have spares.
One way to keep things straight without carrying too much bulk, if you are using the Zone System or something like it, is to have one box with a system of dividers with tabs that you can feel in the dark. I put one tab on the top edge of the top divider, and then tabs down the right side for +2, +1, N, -1, and -2. If I'm going for long enough that I'm shooting lots of film, I can split the stack into new boxes as I empty them.
Also--you don't need to post the same question in more than one forum. They both come up in everyone's "new posts" view.