I don't know of anyone who has done that with a parrot, but I have no doubt they would be able to understand how they worked and link the buzzer with the consequence.

An issue might be the parrot quite simply destroying the buzzer before they learnt to press it and worked out the response!

If the buzzers used are to big, look at the aids for blind and partially sighted people. There are a number of things that you put on top of food cans or clothes hangers and you can record what they are and pay back at the press of a button. They need a fingertip of pressure rather than a dog's weight, so might work well?