Two places to look at that I can think of right off is RealTruck.com and TruckChamp.com. They have OEM replacements as well as add-on mirrors. I want to say they also have adaptable mirror kits to convert standard mirrors to extension type cargo mirrors like is on my F250. Your door panels should already have factory holes drilled for mounting cargo mirrors. Unless you plan on replacing your TV soon, the initial cost shouldn't intimidate you.
Oops and sorry if I'm wrong. Wouldn't hurt to look though.:B