emergency stash
A stash of somthing (typically money, drugs, or lucky charms) that you save when you have plenty of it for times when you don't have any of said items.
"im out of money... looks like I need to get into the emergency stash"
Emergency napkin stash
A collection of napkins, often from various fast food restaurants, stored in the center console of an automobile for use in emergency contingency situations.
I sneezed and spilled my coffee, so I reached into my emergency napkin stash.