Of note, the "camel bladder" term refers not to the shape, but to the material from which it was made. Animal bladders have traditionally been used for fashioning drinking flasks, enema bags, and other liquid-containing vessels. A dried, tanned, but unmoulded and unpainted one is depicted here.
http://www.museumofleathercraft.org/Leather-Objects/ethnographic.htm, via Scribal Terror
Thanks.