As with their last few exclusives, Hastings is rolling with yet another snow theme for their 3rd cover. This one popped up, and sold, over on Ebay. It may have been a leak, or someone selling a pre-order early, but we haven't posted that cover yet.
There isn't a listing for it on their website, so it might be another one you need to actually go physically pick up! I don't remember any online listing for the Rainbow Dash variant they had for the 1st either, so it's not too surprising.
Anyway, good luck tracking it down once it officially releases in a few days!
Thanks to Evan for the heads up!