There are plenty of resources for the metal reed you are referring to. It's called a JC Products reed. It is the mainstay for enclosed reed calls.
As far as the lipsqeak maginifier, you got the basic idea. It's a magnifying funnel. Now, the exact diameters of the exhaust and entry is something you'll have to play around with. It took me a few months to settle on the right combination.
My biggest advice: Watch when working with antler. Drill bits grab and something is going to twist. Either the drill bit will twist off, the antler will shatter, or your wrist will twist. Be careful.
Have fun....Tony
