This post contains affiliate links. OzBargain might earn commissions when you click through and make purchases. Please see this page for more information.
Found these two on Amazon, unfortunately the DLC for Dead Island is not on sale on Amazon, but Gamersgate is having a Dead Island weekend, 60% off Dead Island and DLC. So basically you could buy the game at the same price as the one on sale at Amazon but get the DLC cheaper.
Note: Both games activate activate on Steam.
Extra Note: You need a US address to order/download these games.