Online digital media "shopping cart"

[themeaty]

This is probably a shot in the dark, but hopefully someone might have an answer:

 

A telco I'm working with is using a Windows Media Server to host several locally-produced video streams of high school sports. They want to charge folks to watch these streams. Plans include seasonal passes, month-by-month subscriptions, and per-event.

 

Based on this info, is anyone aware of an excellent "shopping cart" focused on digital media rather than tangible goods?

 

Thank you!