Free is a good price.
This may seem a little weird, but it's free. I found that the shallow boxes from "Bob's Red Mill" products are just the same width as most ribbon spools.
The Bob's Red Mill oatmeal, granola, flour et cetera is sold in small bags. The bags are displayed in shallow boxes on the grocery shelves to keep them from rolling over or getting mixed up by customers.
I just ask a clerk or a box boy if I can take an empty box. Took a little while, but I have collected a lot of these boxes. You can always decorate the boxes with paper if you like.