product options in shopping carts

First of all, sorry if I missed this being in any other posts, if so I simply didn’t see it.
I need a simple shopping cart plugin that has at least one set of product options, in my case t-shirt sizes. I trief various plugins but using a full blown shop system always messed up the pretty simple page design.
On the other side, just adding a “buy now” button doesn’t let the user pick the size he wants for his shirt. and with 3 different shirts in 5 sizes I can’t just type out every configuration and add 15 “buy now” buttons.

Is there any simple paypal based checkout plugin with that sort of option?