We are manufacturing a product (in the USA or Canada) and need a barcode for retail abroad (e.g. Mexico)First of all, outside the USA or Canada you will have to put an EAN barcode on your product that replaces the usual UPC barcode. While it's basically possible to have both codes on a single package it's not recommended. Usually you will have different packaging for foreign markets anyway so this shouldn't be a problem.
Re. obtaining an article number for your product you have two options:
1. Get a manufacturer prefix from the target country's GS1 branch (see below for links).
Assign an article number for your product, create an EAN barcode and put it on your packaging replacing the usual UPC.
2. If you only have a single trading partner in the target country you might be able to obtain an EAN number from your partner. This can either be a number from their stock of EAN 13 GTINs or it can be a EAN 8 number if the product in question is only used within the respective organization, e.g. super market chain.
To find the GS1 branch for export destination, see the list on the GS1 website.
EAN Barcode SoftwareWindows PC - Softmatic® BarcodePlus (Win, V4, Windows XP or higher)
Download for Windows
Mac OS X - Softmatic® BarcodePlus (Mac, V4, 10.7 "Lion" or higher)
Download for Mac