Don't know where you're located, but it is possible to get some chert or flint from natural deposits and make your own gunflints.
I've done a little on that line, it takes some practice (ok, lots of practice) and at the start my waste to keep ration wasn't too good, but it's getting better.
I only have a small supply of raw flint, and I bought that. But I've been studying geological reports for my state and have located a couple large chert outcroppings about 2 hours west of my house (mostly on public land, so trespassing isn’t an issue). Haven't been able to get a free weekend to run down there and see what I can find. If it's free, I'm not too concerned with my waste to keep ratio, and with more practice I'll get better anyway.
There WERE 2 small chert outcrops in my county (small, as in the larger one was 200 feet long by about 6 feet wide, and the small one was reported to be less than half that according to old geology class field notes I dug up from 40 years ago, but unfortunately when I tracked them down both were inaccessible. One is now under a recently built sub-division, and the other is under an interstate highway.
So if you can find natural flint or chert that you can pick up for free, and learn how to knap flints yourself, you’re all set! No more paying $2 for a flint! It's also cool to use stuff you made yourself. I'd make my own black powder, except that's illegal. Sure, my flints aren’t near the same quality as the best commercial ones, but they work fine, and they’re free!