You should check out Extreme Economies by Richard Davies. It's a book describing economic systems in extreme situations. I do not remember if it has a specific chapter on prisons though.
Deep Aside: EconTalk's episode on Richard Davies' Extreme Economies is really really good (and long!).
The section on how Angola Penitentiary's underground economy changed overnight from Cigarettes to Ramen/Mackerel and Bitcoin-like-cyphers is amazing stuff.