When making a wing bone call or even a cane yelper where would one get that mouth piece, the piece that would bump up to your lips. Are the black ones a piece of neoprene ? Some look like they are carved out or cork.
Some makers use a rubber stopper sanded down to shape on their lathe. Cheap and easy can be a black faucet washer. You can use a natural cork. All of these are pretty easy.
There are actually some for sell in the trumpet turkey call section on ebay. Never seen that before.
I turn mine from rubber stops or foam
You can turn rubber stoppers, or cork rounds or EVA foam on a lathe or drill using sandpaper to form the shape.
I used the beveled faucet washers for years and they are the easiest and work well.