[expired] Kids Woot has Halo Microfleece sleep sacks for $9.99 (50% off list price). Right now they have small, medium and large, and there are six colors to choose from.
KidKraft wooden toys are in one of the pop-up shops at Kids Woot, so you might want to check that out while you’re there.
$5 ships your entire Woot.com order, so buying more than one sleep sack gets you the better deal (obv.).