More about Substitutions

Any laceweight yarn will work. As long as you know that a 100% merino, alpaca or silk will give a less ethereal look and won't be disappointed by this you can try the following, as suggested by Crystal & Stuntmother.
KnitPicks Shadow, Gossamer, Alpaca Cloud or Shimmer
Schaefer Yarns Andrea
Crystal Palace Yarns Kid Merino

These yarns have some fantastic colours!!! If the 1st Butterfly knits up great good not horrible, I'll have to seriously consider doing it again. mmmmm - silk!!

Not having worked with the Kid Merino, I can't speak to it's blockability, Crystal, but it falls into the appropriate weight category. The only way to really know how the yarn will behave - yeah, you know what I'm gonna say - is to swatch it. Even acrylic can be wet blocked. I wouldn't steam it unless you've tried it on a swatch and know what's going to happen.