Here's another one you missed:
MoKo - Slim $5.97 (different style of cover than the one /u/Chezzabe listed)
Though I've noticed prices are going up a bit. When I ordered my case, it was only $2.99 + shipping; now it's up to $12.99 (with free Prime shipping, if you get that). Still, Amazon shows a list price of $39.00, so you're still getting a good deal.