Your brake light switch is a very "stock" GM part, used on many GM vehicles for many years. If you look at Ecklers site, one switch says 58-64, the other says 58-76, it is likely the same on a Buick, Olds, Pontiac, Chev, cars, trucks, you name it. You can pick it up locally at NAPA, etc.
It is a simple button switch, button out you have power to the lights, button in, no power. It mounts on a bracket on the steering column, and the wires that connect to it should be hanging there somewhere. That bracket should be there for you to see, with or without the push button switch, the button goes up against the side of the brake pedal facing toward you when you are sitting behind the wheel. You need the bracket to mount the switch. If you find the 2 wires, tape them together and your brake lights should be on, if you want to make sure they are working while you wait for a switch.
Like Dan says, much of the new stuff is poor quality Chinese stuff and a good used part is very often better. If you have a good junk yard close by, go there and get familiar with what they have there. Take pictures of any cars there and of any cars you get parts off, it may help you to look at them in future when you need more parts or need to figure out how something fits on your car.
Take pics too of all of anything you are working on before you take it apart, very helpful to put it back together. And, if you have it apart very long and can't find a part you think you took off, you can see if it was there in the first place.
Take pictures of all the area under you dash by the brake pedal and post them here, we may be able to see what you are seeing. If you have the shop manual now or soon, the wiring diagram is coded to tell you the colour of those 2 wires that go to the brake light switch.
Keep asking questions, we all love to answer them.
Don