E-Commerce with Merchandising Solution

Hy there!

I was wondering if there is any service that combines e-commerce services like fastspring.com with merchandising stores like cafepress.com or zazzle.com.

The ideal way for us would be a pay-what-you-want option like pop has (http://www.popme1.com), when you pay less then X dollars you get the downloadable game, when you pay more then X dollars you get the game and a shirt. All should be handled by one service provider.

I think "Pop" asks the customer for his shirt size with a custom survey from fastspring and then has to order the merch manually for every customer. Is there a more convenient way to do so?

Thanks in advance!