Interactive product availability

Hi,
I have a tricky questions to which I can’t find an answer:
I’d like to offer a downloadable product (text and photos) to my customers (newspaper editors) in two versions:
1. syndicated – meaning the buyer purchases the product for a reduced price, knowing that others can also purchase it and use it for their newspaper
2. original – meanig the buyer purchases the product at a higher price, knowing that nobody else can purchase it and therefore it’s unique content for his newspaper
And here’s the tricky part:
– As soon as one person chose the 1. option, the 2. option shouldn’t be available any more, but unlimited more buyers should still be able to buy option 1.
– As soon as one person chose the 2. option, neither the first nor the second option should be available anymore.
Does anybody have a clue how to achieve this?
Thanks a lot!