You may notice that some games rely on a bell and others rely on a bell AND a Buzzer. The bell is pretty easy to find at most hardware or stationary stores, but the buzzer can be harder to find.
This is what I recommend:
The buzzer from a Hasbro game called Taboo. The buzzer can be ordered at this site. Order two of them, one as a back up.
However there are other sources for buzzers. You might also try a bike shop or an electronics store.
You can place both of them on a small board (1/2 inch x 10 inches x 12 inches) and secure them in place with a few screws.
When you play games that require a ding and a buzz (like “Family Dinner”) they’ll be together.