If you look at this link you will see two TSN catfish in the same tank. http://www.planetcatfish.com/catelog/image.php?image_id=2027 One is from the Amazon
Basin, the other is from Venezuela-Peru-Paraguay. Both color morphs are referred to as TSN. If I am not mistaken, he wants the one more of a pattern from Venezuela.
Because the common names are shared and it is highly possible that the latin names are used interchangably, it will be very hard to find one for sale online and be 100 % certain that you will be getting the right color morph. You could try www.sharkaquarium.com or any other site that offers TSN's for sale, but be sure to ask for a picture of the fish before you buy it. I know it isn't much help and I hope you find your fish. I know from experience that it is very hard to find the right one without seeing it first.