any sailing shop will help you. 4mm spectra should do the ticket. this stuff is strong

i know yacht grot in fremantle have heaps of differnt types of rope, if you go there the should sort you out. The thing is with some cheaper ropes is that they strech, which isn't always good when your are overpowerd as when the rope streches its makes the sail more fuller and the sail becomes even more overpowered.
from memory its about $2.20/meter, which is peanuts really

surf sail is closer to home for you stiffy and they got the rope your after, i was just there on sat purchasing my new pride and joy mast

GONE WITH THE WIND