I noticed that there is an upcoming interest in Rousseau harmoniums lately on the forum.
I have knowledge of a very big instrument which is currently for sale. I was interested in it myself some time ago.
The seller is not an easy man, and at the end I just gave up.. don't expect it to come cheap.
some pictures (mind the 3 harpe eoliennes)
Send me a PM if you are interested, it's for sale in France.