The yarn recommended for that sweater is Berroco Zen, which is described on this webpage: http://www.berroco.com/shade_cards/zencolors_sh.html
It looks like a ribbon yarn to me. Do you have a local yarn store where you could look at the yarn? You could either buy that yarn, or you could try to find a similar yarn somewhere else. The design always turns out best if you use the recommended yarn. But, if you can't do that, at least you'll know what the yarn looks like, so you can make a decent match.
You could also try finding a yarn that knits to the same gauge, which is the following, using a size 9 needle:
4.75 sts = 1"
19 sts & 23 rows = 4"
So that means, the yarn knits 19 stitches for every 4 inches.
If you want to find a Lion Brand yarn with that gauge, just look at this page on their website for yarn substitutions.
Look at the description of each yarn, and try to find one that knits 19 stitches for every 4 inches. (Looks to me like that is a medium weight yarn.)
This page shows all of Lion Brand's medium weight yarns: