I've was thinking about a flinter myself but now I'm planning on going with a Traditions Hawken percussion kit.
Look at the Traditions brand stuff, it's the lowest price and probably most available. They have a few models around $360 to $420. To get real walnut you need to spend more money nowadays.
From what I understand, you should have a clear understanding on what you want to use if for before you choose your muzzleloader. If you're only going to shoot round ball, look for a twist rate slower than 1:60. If you're going to shoot some sabots and some roundball your twist around 1:48 would be a compromise between them both.
You can go to the Cabelas website and browse the blackpowder and muzzleloader sections to get familiar with what out there but they're pretty much out of stock of all flintlocks from what I can see.