Upgrade from Chinese to International

I'm using DOpus' Chinese standard version, now I want to upgrade to Pro, but both of the two reseller don't have the upgrade on sell, is there another way to upgrade?

Please email sales@gpsoft.com.au if you have a question relating to licencing, purchasing or upgrading that isn't covered in Common purchasing, upgrading and licensing questions

They can probably help out, although I don't know for sure as it's not my department.