I know they make the Look out for multiple dogs. I used the standard one for my 10 pound and 4 pound girls and they just snuggled up together.
Here is a link for the standard size:
http://www.petedge.com/shopping/prod...ctID=3326&AS=1
And one for the larger size:
http://www.petedge.com/shopping/prod...ctID=3325&AS=1