Some people are still making them....somewhere. I saw a new one for sale on ebay last week or two weeks ago for like $8.00. It was the built circuit and switch and wires...then you install it inside your mic or radio.
Or you buy one from somebody who has one. There was one installed in a D 104 for sale here a few months ago for $85. I don't recall it selling and the guy may still have it.
Post a WANT AD in the for sale forum and see if somebody offers you one.
You can also make one yourself. Here's the schematic
Tweety Bird Noise Toy Schematic
good luck
oh yeah...and I want a full blown tweety bird array too, with 3 buttons and 2 switches and the variable pitch control....yeah baby.