I have been told that they will do custom fit breathables right here in Langley at the BARE factory.
I am thinking of heading over there to see if they make kids waders
For what it's worth, I would never buy Bare again....
I finally gave up on my pair after they leaked on the seams the 4th time out... this was the 4th pair I had (warrantied them 3 times!) They are hanging in a closet right now, as they have for the past 3 years, and will probably be made into rain pants...
My buddy just bought a brand new pair of their newest model this year, and his seams just blew out, freshwater fishing, on the 4th trip out as well.
So in short, don't spend money getting them to make you a custom wader. I'd go with Sea-tux as nicefish said, or try cabela's out.