A friend of mine, who is also a proud new mommy, saw this cute kimono style top my little caterpillar was wearing in this picture, (actually in lots of pictures) asked me where to buy it. We got it from China. Little caterpillar's great aunt sent us a couple of boxes of baby stuffs when she was born, and they are so beautiful and practical. These kimono tops are what Chinese babies usually wear, but we normally call them monk tops instead, and they have matching pants too. Instead of gorgeous Japanese fabric, these are made with very soft cotton, and 100% cotton batting, just like a quilt. So, it's very comfortable and warm, great for New England winter. I have never seen them here in US, but I think they are quite easy to make. Here are just some tutorials I found online. They are all just one layer of fabric, but you can easily quilt them first and then sew them together using the patterns, or make a couple of them and sandwich another made with cutton batting, then quilt them. I think either way will work.
Kimono Tutorial from habitual.
Empire Line Kimono pattern.
Kimono Top knitting pattern.
I also found this one which is very interesting. I really like it, if I have some extra time, I will definitely make something similar to this for my little caterpillar.