I went to both gamestop.com and impulsedriven.com and none had any listings for Inversion.
Here you go
Thanks, that's probably you're only way to play the game, alot of PC games are download-only in America it seems (Risen 2, Binary Domain, Dark Souls, Blades of Time), as for me that's what this page tells me:
"Sorry, this item is not available in your region." (I am in Europe), so I'll get the retail version of Europe which is gonna be released the 13th July 2012.
Well at Gamestop you can get a rubber ducky, a water gun, or a pirate sleeve Wii bundle.