I just checked on Ravelry and here are some of the yarns that people have used to make that sweater:
Debbie Bliss Baby Cashmerino
Debbie Bliss Cotton Cashmere
RYC Cashsoft Baby DK
Dale of Noraway baby Ull (that one is soooo cute

)
Blue Sky Alpacas Sport Weight
Rowan Wool Cotton
Sirdar Snuggly DK
Obviously there's a bit of variance as far as yarn weight goes...but with a baby pattern there's a little room for that, IMO.
