You can still get them!

After 4 hours of refreshing, I finally got mine! if you haven't tried it yet, this is the link that got me through the best: http://na.merch.riotgames.com/en/checkout/onepage

This page can freeze up and stuff, so be careful. I don't recommend refreshing the page if you get through, but if the checkout page freezes up on you, try opening it again in a new tab.

Good luck guys!