Okay, so…the “deciphering whistles” page of Chiff and Fipple declare A-flat whistles to be rare, and doesn’t identify any manufacturers. I know I can kinda-sorta fake the key of A-flat on an E-flat whistle, but what I really want to know is…does anyone out there own an A-flat whistle? And also, does anyone manufacture an inexpensive A-flat whistle?
This topic came up today in a group I play with - It would be a nice key for a couple of us.
Interested in hearing what’s out there. 
If I needed an odder whistle, the first person I would ask is Mack Hoover.
http://larkinthemorning.com/product.asp_Q_pn_E_WHS095D_A_Chieftain+Pennywhistles_E_
According to Lark in the Morning, they carry Cheiftain tunable A-flats.
You’d be much better off just to have Mack (or anybody else) make you one.
Try Syn whistles here in Australia. Erle makes a variety of whistles that sound great and are priced very reasonably! Recommended.
Teflon
Mike Burke makes them. I suspect Overtons are available in Aflat, too.
Whoops - I read the subject line and opened the thread expecting to see a story about a poor whistle that had been run over, stood on or otherwise squashed. A flat whistle. 
Funny how ones perceptions can skew things 
You are not alone, Chris! I almost didn’t read it, because, I really didn’t think a flat whistle was that I was interested in!
How/where do I get more info on the Syn whistles?
Chris, I was right there with you looking for a bit of comic tragedy … er… tragic comedy… er… well… the story of how someone flattened their beloved whistle (or one they really hated )
I came close to doing that with my poor little ole Gen G… it looks like the adventure should still be clear in what passes for my mind… but, alack and alas… it is a tale long forgotten… I’m waiting to come flush agains so that Jerry can see if it is tweekable in it’s stressed condition.
So… now the topic can fill both bills??
You can email Erle of Syn whilstles here.. synwhistles@yahoo.com.au
Drop him an email and ask him.
He doesn’t have a web page unfortunately as word of mouth seems to be enough. He is very helpful and if you are in America due to the exchange rate I think his whistles would be quite cheap for you. I’m in Oz and I still think they are very reasonably priced.
Teflon
Just check out my avatar - that’s a flat whistle for sure 
We don’t make A-flat whistles, but we do make G#
Which size High or Low (Alto)?
One time I used some K&S rectangular tubing to make a flat surfaced whistle - it works pretty well although the feel of finding the toneholes is kind of weird.
I had a go at making one A flat but it spoiled the tone
This is amusing. I started a thread once in which I asked if anyone owned a whistle in Ab, Db or F#. On that occasion I didn’t get a single yes. I wanted to know if anyone recommended any make in particular since certain makes are very well known for being good in particular keys.
Ab would be useful for anyone who plays blues with horn players as Bb is a very popular blues key with sax and trumpet players.
My Ab is a Water Weasel - and I love it! The others mentioned here are also good choices for it. I use the Ab a lot - especially in Church where I tend to hit a number of hymns in the flat keys…
Cal
… and clarinets!