- there are plenty of people here on moodle that would be willing to create something for you - especially if you would be able to put some funding towards it. - if you would like to pursue this option, have a look at moodle.com - there are various partners that would be more than willing to help!
Dan
I have a constructive suggestion, but first can I suggest that the Prisoner's Dilemma is quite counter-intuitive (particularly in its standard 'two accomplices to a crime' format) and I'm not sure how much learning students will get from interacting with one another rather than a computer opponent with a set strategy. People generally don't like 'betraying' others that they know, even if it's only a game, which takes away from the rationality needed for the PD to work.
I'm sure you are aware that there are several websites allowing you to play the Prisoner's Dilemma (and the iterated version) against computer opponents.
Anyway, my constructive comment is:
Each game is played by 3 students. Two 'prisoners' and a third 'jailer' who applies the rules of the game and gives out the rewards. The 'prisoners' therefore can use any of the communication tools in Moodle, or even plain email, to contact the 'jailer' once they have made their decision and she in turn can send back the results. The students can then switch places, each taking their turn at being a jailer.