No, not every product is available in every domain. For a complete list of what is available in each domain, visit each domain’s Custom Gifts page.
https://www.zazzle.com/custom/gifts
https://www.zazzle.co.uk/custom/gifts
https://www.zazzle.co.jp/custom/gifts
And so on.
To see a complete list of Zazzle domains, click here - https://www.zazzle.com/international