I live in limestone country - lots and lots of limestone deposited all around here in the Upper midwest US. So the "flint" I find is usually associated with the limestone. The local stuff is more grayish to white, and closer to the coarse Chert than the glassy Flint. But it does work with the traditional flint strikers I make.
Flint is just a Hard, Sharp stone edge used to chip out little bits of steel from your traditional flint striker. The energy put into chipping out those little bits of steel heats them up enough that the carbon in them burns. That's the sparks you see.
But other stones will also work. Flint just tends to get a better sharp edge, and hold it longer in use. Chert is softer, and that sharp edge will crumble back faster. Granite will work, but it is harder to get a thin/sharp enough edge, and it crumbles faster. Quartz will also work. Some fancy historical flint strikers had cut/shaped/polished agate and jasper with them to use. In the right conditions, some slate will even work.
That rock is just the hard/sharp edge to chip out the steel. So experiment around with some of the rocks you do have around. Some just might work well for you.
One other note about flint. When you look at the original "rock" as it is washed out of the chalk and/or limestone, it often doesn't look like flint. It quite often just looks like all the other rocks around it. The true tale is told when you break it open. The insides are often quite different looking than the outside. That outside is quite often covered with a whitish or tannish colored deposit that hides the inside. The flint from the chalk cliffs have that white layer on their outsides. The smaller flint nodules in the Southern "flint" areas of England often look like round balls with a rough yellowish outside. But when you break them open, they have that gray/black glassy insides. So don't judge a Rock by it's outside. They often hide other things inside.
In many areas of England, you can still find houses with the walls covered with rocks. Some of these look like round gray/black rocks with the outside mostly flat. These are often flint rock. The round "ball" type nodules were broken in half, and then applied to the wall with that flat inside showing out. That usually means that there is a lot of flint in the area. Just don't go chipping a rock off of the walls of somebody's house!
Good luck on your quest. And do try some of the rocks available in your area.
Just my humble thoughts to share. Take them as such.
Mikey - watching some of the "mineral assets" around here get hydraulicly modified/moved/repositioned
(it's raining, and washing/flooding in the valleys)