The best one I found is the BINA 23B Deluxe which I got from Keshav Music Imports. He used to deal out of his apartment on the Lower East Side here in NYC but now he has a store and web site -
http://www.keshav-music.com/harmoniums.htm
What I like about dealing with him is that he inspects every instrument for build quality and sound.
Make sure you get one that is tuned to A440 - just makes it more practical.