Translation missing

Hi there and GREAT THEME!!!!
I have translated the POT file, but quite a lot of terms/words are missing in this file.

Applying e.g. coupon functionality in the cart is no where to be found in your language file.

How might I go about including the missing terms and translate them?
Is it only available in your premium version?

http://wordpress.org/plugins/wordpress-simple-paypal-shopping-cart/