I had the Key West decks made with Liberty Playing Card Co., of Arlington, Texas. They're plastic coated paper cards and compared favorably to a deck of USPC "Aristocrat" plating cards. They have several card stocks, and I selected their Imperial Linen card stock. Liberty will do very low numbers.
For plastic, I would have gone with Joe at Palm Imports / Palm Gaming Inc. He sent some sample plastic decks which were very high quality -- nice material and an absolutely perfect printing quality. (Palm makes cards for real casinos, so you simply can't get better plastic cards.) Some time back, Joe stepped back from direct contact with customers, and Palm now employs several reps to contact customers. If you get in touch with anyone at Palm, they might consider doing your decks.
I went with paper decks because I felt they were more in line with the retro theme of the Key West.
I'm sure you're realizing that quantity will be a major factor in getting custom cards. The big card producers (USPC, Gemaco) need an order for 10,000 when I last checked. It may be more now.
Small producers will do anything from a few to a few hundred decks. Most of those producers are making novelty decks -- great for wedding favors, but you'd never, ever consider actually playing poker with those decks. They tend to be really stiff, and impossible to shuffle and deal. Others are so thin you can actually see through them.