You need to obtain your numbers from local GS1 organization (
http://www.gs1.org/contact). You will pay annual fee to get your company prefix, and you fill the remaining digits with item number. Combined the two you get EAN-13 number.
Some companies sell their spare numbers online for a small fee. Those numbers may be used if you only have a few items. However, some big retailers such as Walmart now asks for proof that you “own” those numbers. If you need to ship to those retailers you will need to get company prefix from GS1.
The information above is provided "AS IS", with no warranties, and confers no rights.