The question has come up in the past here on Chiffboard, but I think thus far without answer… UNTIL NOW!
For anyone interested in the tiniest of all whistles, a fellow by the name of John Orth up in Golden Colorado makes a very nice little bird flageolet. No website as far as I know, but he does sell through Ebay, and has some of his work up on Deviant Art (http://orthwest.deviantart.com) and can be reached by email at orthwest@gmail.com.
I have to say, the aluminum recorder looks pretty spiff, even if this is Whistleland!
The bird flageolet is in wee-tiny g, which puts it a fourth above Mr Bingamon’s whistle in wee-tiny d and therefore an octave above your average high g whistle. For all that, it is playable and you don’t have to have the wee-tiny fingers of a three year old to do it!
Lovely whistlesmithing! (Bird not included with purchase.)