I would second the suggestion to call Mr. Copeland directly. I buzzed
him to buy some Sweettone whistles and asked him if he could make some
adjustments on another whistle, not one of his. He did the work on the
other whistle for $10 (a total bargain!) and sent the new whistles. It
took about a month.
He is a very nice man who loves to talk to other flute/whistle players.
Give him a buzz.