You can buy wire pretty much anywhere....i usually get some at home depot. Much cheaper than what those ripoff "mod" sites sell it for.
And as far as the series/parallel thing, you can actually hook it up into parallel much easier than in series.
Doing it in series will just be a hassle, and if you bend it to much you are likely to break off the pins from one of the LEDS. And in series, if you break one of the LEDS the entire chain dies. In parallel everything stays working.