amazon won't generally ship pyro - which is why i linked to the guys site in the uk who will probably ship to the us.

Nope cant find any listed.

Your best bet is to find a local hobby shop that does rocketry.
What you are looking for is visco cannon fuse. 

Should be us suppliers.

lol: https://www.cannonfuse.com/
try them
Specifically this: https://www.cannonfuse.com/store/pc/Chinese-Visco-Cannon-Fuse-2p518.htm

$1.75 for 10 foot that burns at 25 seconds per foot - ie: very slowly.


Light, throw - 2-3 seconds, flight time 3-8 seconds. length of fuse needed - around 4-6 inches

In making clay ammo, just stick one end of the fuse into the wet clay and let dry.

depends on how you attach the fuse to the missile.
Generally the fuse doesn't touch the pouch.
Leather is fine, you might get the odd scorch mark, but it takes a lot to burn through leather. Should be fine