"I have been afraid that the exotics are too fragile for a bike seat....Bikers are not know as the most sensative guys when it comes to the treatment of their "ride". Watch 'em do burnouts sometime..... Laying rubber until the tire catches fire and blows out.....Not sure that guy is going to be happy with the durability of a beautiful alligator hide insert in his seat."
Try shark, elephant (main body), or stingray - all very durable skins. Elephant ear and trunk are available also, but are thinner and thus less durable. Ostrich would work, too, if thinned down and then adhered to a 3/4 oz (minimum) piece of veg tan. Stingray can be a pain to sew at times, depending on the means you do it by. A needle and awl machine has fits with it, hand sewing would be absolutely no fun either. I have a couple Artisan Toro 3000s and have had no problems. The shark, ostrich, and elephant are soft - just like leather - so they're easy to sew.