Hello,
do you know where to find Avatar game from 2009? Not on Steam. Not on GOG. Not on Ubisoft store (despite being a Ubisoft game). Not on current consoles (only PS3, XBOX 360 etc.)...

It's a licensed game so the Avatar license expired and wasn't renewed. (maybe GOG could try now that Avatar 2 is coming out but I wouldn't expect anything :P)

Amazon and eBay might be your best bets, unless shipping is a real pain price-wise for you. I suppose you could try your luck with "other sites", but I also can't vouch for if the ISOs/roms from said sites don't have some -ware in them (not sure the likelihood of that though), so use caution if you go down that route.

Retail versions (PC, Wii, XBox360, PS3, Nintendo DS):
https://www.medimops.de/produkte-C0/?fcIsSearch=1&searchparam=James%20Cameron%27s%20AVATAR%3A%20Das%20Spiel

Retail versions (PC, Wii, PS3, Nintendo DS)
https://www.ebay.de/p/56270986