Having used a change bag for many years I have decided that using my top hat would be a more convincing change. I have searched far and wide for information about making one but short of buying the various wizard's hats available I cannot find a top hat/change bag. I have prototyped a couple of top hats but cannot get the change mechanism going well. Does anyone have any ideas?

Bev Bergeron, I believe was the first to come up with this idea of a change bag top hat (early fifties???).
It has been published in a lot of his lecture notes, unsure where you could find them now though...
I believe Bev went thru quite a few different prototypes before he came up with the version he currently uses.

He has the best plans I've seen for a change bag top hat.

Top hats cost over $100, It is an expensive change bag.

Or maybe one of the $45 dollar models will work.

Thanks for the advice. I have contacted Bev and hopefully he can help. As regards the 'expensive change bag' I agree top hats are expensive. I use Butterick Pattern #3664 and make my own. The top hat is the 'floppy' style which suits my character. I am currently working on a themed show which involves hats - I have hat tables, Alakazam Hat(square/circle), Hats and Ball routine, Rabbit out of a hat. I got the idea when I found mini top hats in a craft shop which I used once for a 'pea under hat' routine.
I've always thought a change bag to be a bit 'special' whereas a hat is part of the costume. The other reason is if I do an egg bag routine - one bag is enough per show.

Follow up:
Thanks Malini for your help. Bev Bergeron is alive and well and has been very helpful. I have been sent a copy of his notes. When I complete the hat and perform with it, I'll post my experiences and thoughts.

Bev gave me a bit of history:
He first published the idea in the Linking Ring as a vanish of a dove in a top hat -- that ran in about 1959 and again in the early 1960s. This used a nonfolding top hat. Later he started using a folding top hat and found that it worked great for changing items. He first used it in the early 1960's for the Sun & Moon Routine. The hat has since been a tool for Bev for many different magic effects.

Visit his site at: http://www.bevbergeron.com/

Hi.It sounds like what you want is a devant hat changer.
this is a flap that fits into the crown of a top hat, or bowler hat, and is the gimmick that made the clasic " a girl, a boy and some eggs" possible.
this was invented way, way before the 50's by the way.try the late 1800's and your close!!
Dale

I have since purchased and received Bev Bergerons notes "Bev Bergeron Down Under" which details his change hat. The notes he gave on the top hat changer were scant and really no more than an idea. I was disappointed really, as what I received added no more understanding than what I had already derived for myself.
So I have since produced a prototype which works extremely well, kids can put their hand in the hat and feel around no problems, this is one limitation of the Devant Hat Changer.
So I guess my quest for detailed plans for a top hat change bag continue or perhaps I'll publish my design one day...