For anyone looking for a small quantity of cheap, white-colored corrugated stuff for cartridge drawers - I came across this listing on Ebay for 9" x 9" pizza box liners:
I used the “make an offer” option and offered $9.95 instead of the listed $12.95 and he accepted, so for just over $20 shipped you get 200 of these squares. I’m not 100% sure about acid content in paper or whatever, but I am going to try them out. They are coated with something I assume since they are supposed to be grease-resistant for pizzas.
Should I be concerned much about possible chemical content in the paper touching brass?