Ebay also has some reasonably priced decent ones.
If you've had a few of them then disregard, but if this is your first one I'll offer my preferences. I will also say that there is a tendency to buy too big of one for your first because you think you need to carry a ton of stuff, and will later wish for a smaller one.
The perfect one for me would be about a 6" bag of stiff leather so it keeps its shape well, has a divider splitting the storage space in half on the inside, has another small pocket for holding small items like a nipple wrench, jag, etc., and has a loop on the outside for a short starter (I don't keep it there if hunting in brush, it's just for repeated shooting). I'd add a patch knife sheath to the strap if I was cutting at the muzzle.