You are in Kentucky, there is lots of flint and chert there .You don't need big chunks. Or a lot.
Part of the fun of buckskinning is sourcing your own things from nature. Go for a walk with your fire steel, and check out any rock that looks like it may spark. I often end up with a pocket full of rocks to break for fire starting.
I'm in the northern Rockies, and flint and chert is very rare here. However, I find lots of quartz that sparks just fine.
Iron pyrite (fool's gold) sparks well, even if it looks rounded with no edge like you need for flint. Any rock with a smooth glossy look is a good candidate for sparks. I even use obsidian at times. It's not the best thing to use, but it works.
Any time you start breaking flint, expect a lot of waste, although for fire starting you will have more usable chunks than if you were making rifle flints.