You can presumably order the official part from Kerk Motion at
http://www.kerkmotion.com/products/l...howtoorder.asp
I suspect the kit part is identical to a precision modified-acme threaded rod, size 1/2"-8, 4 Starts. In which case it can be had from McMaster Carr. But only in 6 foot lengths for $128. If you're interested in that, the part number I'm guessing is 6350K23. The matching nut is 6350K43. It might be easier just to get two of the nuts and use all McMaster stuff in that case.
Alternatively, you could ask around for teams that aren't using their lead screws. I'm pretty sure we aren't. I know there's not too many hawaii teams, but one of them might still be able to help you. Then you just have to contact Kerk Motion for a price for your BOM.