Don't even go to the old DC-DC converter. Since it's decoration (at least this was the case in 2014) you can use anything you want to power these things. Seriously all you need to do is look on hobbyking.com for a BEC. There are like 20 of them that output 5a @ 5v. That should be more than enough. And if you need more, you can get a Castle Creations 20a 5v (If you need this you are doing things very wrong).
And the best part is that they weigh under an ounce! I have ran plenty of neopixels on these guys before. They work perfectly every time.
If you don't like hobbyking for some reason, you can always search up on pololu or amazon for a 5v BEC or Buck converter. Super cheap and light stuff (Unlike the old dc-dc converter)
http://www.hobbyking.com/hobbyking/s...dProduct=62640
(Note: They may have changed the rules for this upcoming season. I am sure you would be fine ordering these, but still make sure they are in the rules