Hello everyone! Can someone please help us find out how we can add USPS First-Class International to our USPS shipping methods? According to the USPS Web Tools support, they do offer "First-Class International" as an option and we must upgrade our USPS shipping module to use it. How can we do that?

We're using the version 1.3.7. and this shipping method (First-Class International) does not show up in the options list on our Zen Cart admin panel? We only have these choices for International shipping:

GXG Document
GXG Non-Document
Express
Priority Lg
Priority Sm
Priority Var
Airmail Letter
Airmail Parcel
Surface Letter
Surface Post

We really need to use First-Class International. Can someone please help? Thank you.