ask around at marinas and boatyards to see if anyone has an old junked sailboat they're gonna scrap. you're gonna be looking at a few hundred pounds of lead from the keel and ballast, if you have the equipment to haul it off. check out your local range as well to see if you can sift old bullets from the dirt. either bring a wooden box with mesh on the bottom to separate out the lead from the dirt, or do like this guy in this video.
as far as propellant, it may be possible to use match heads, but you're looking at less powerful, less reliable ammo, and it may dirty up your gun. i'm also not sure how good that kind of residue is for your gun. it may be corrosive like black powder.
if you're worried about SHTF, stock up on good, reliable powder. matches would be too useful as regular fire starters to waste like that in a survival situation.
another tip: save your spent primers, corroded/cracked cases, and any .22 cases you find. you can't use them for reloading, but they're valuable. sell them to your scrap yard guy or trade it to him for tin and maybe some high antimony lead alloy.
finally, go ahead and scour youtube for videos on casting, reloading, and powdercoating bullets. download as many as you can before youtube purges them.