you will need an ebay account with paypal
German ebay allows the sale of game and software license keys, Australian ebay doesnt, Australian ebay even blocks key searches
anyway goto www.ebay.de and search for windows 10 key, you will find many hundreds of keys for sale purchase an international key from any of the reputable sellers with thousands of sales,
i personally use bestpreisshop2016, they speak english and always answer quickly, and send key by email within seconds of paying i got my last windows 10 key for 15 dollars from them.
look around though you can find them even cheaper than that
simply pay by paypal like normal to make purchase safe, its not only windows the germans have cheap, its all software, at prices for keys that will make your eyes bulge, many of them international versions with no region lock,
my first deal hope its ok
**Mod: Please see moderation note. **
Just because a key isn't cancelled, does not make it legitimate and doesn't mean that it won't be cancelled in the future.