Zyxel provides different ways for customers to purchase devices or licenses.
The easiest way is to browse to https://www.zyxel.com/where_to_buy/where-to-buy.shtml .
After selecting your country, you will receive the correct website information of the country in which you want to purchase new devices or licenses.
On the top right in the page header of zyxel.com you'll find the menu "Where to buy":
In this menu you can select between the multiple channels for buying Zyxel devices or licenses in your country.