Just standard seat brackets? I think almost all of the vendors sell the Dennis Carpenter product, which is pretty standard.
Then there are pricier, custom, or nicer options available, for custom seats you can use like Corbeau brackets, or something nice for front passenger seat, the LCR seat bracket sold by Duffs.
If you're just looking to bolt stock seats to stock holes, any one of the vendors all sell the same ones from Carpenter, I believe.