Radio Shack?
See this sucks hard because when I was young this was the place I went to get components for my projects, then they left our area. And I don't know if there's any more in England.
We have Maplin's but like you said about 'Shack they have started to sell everything else apart from electronic components!
I go to Mouser now...
If you don't get a piezo buzzer you can use a small speaker.