You can get small capsules in the keychain area at REI for about $3 each. EDC Depot has the one shown and some larger ones too. (https://edcdepot.com/merchantmanager/product_info.php?cPath=4&products_id=168&mmsid=49cf07bfab535780e975cab7ca79aa0a)
Spy capsules are a great way to carry tinder, matches, spare medications, etc. They make whistles with a small capsule as well. The fat ones can hold a nice selection of "MacGuyver gear" like wire, Spectra line, fish hooks and split shot, button compass, matches, sewing kit, scalpel blades, water treatment tablets, super glue-- stuff to keep you alive and make repairs to your gear.