Try woodworker.com or vandykes.com for sources with catalogs that show a lot of stain products. Rockler.com and woodcraft.com have stains in their catalog but without the detail that the first 2 listed show. For something like this, you could also consider something like a Van Dyke brown Japan color mixed to stain consistency.
Annie, you will have to sand your floor to remove the old finish before you stain. You cannot reliably stain or paint over an old finish in most cases. It may last for a while but no where near as long as the original stain on wood and finish process. I suggest that you buy some of the same kind of wood as your current floor and test to be sure that you will get the look you want before you try something on the whole floor and are not happy with it.