[Deefuzz]

Definitely scope local comic shops in your area.

Or if there are any toy/comic shows happening in your area anytime for the rest of the year that would also be a good place to hunt them down.

If you only want to deal online you can try Wizard Universe, they have some but the prices vary dependent on the age of the figure/rarity which kind of sucks. But here is a link to their Blackest Night figures: DC Direct Action Figures Green Lantern

Then there is always ebay...