wp-e-commerce/WP-e-Commerce — pull request #304 by 1bigidea (2013-03-21 22:32:39+00:00)
Title: Buy Now button with Variations (related to #303)

wp-e-commerce.js
when updating on change in selected variance, update the
corresponding Buy Now button

display.functions.php -
include a hidden field in the Buy Now form to pass the variation
value(s) to the Add_to_cart