Selling custom phone cases on etsy?

I've seen a lot of these cases on etsy, with designs that people usually make by themselves on photoshop or something. I have a lot of designs, and more in mind and I want to know if anyone has any idea where I can get these phone cases for a cheap price and how I can put my own design on them. Mainly for iphones since those sell the most but maybe for popular phones like samsung galaxy or htc evos. Thank you