As a former embedded systems engineer, my door bell is two long bits of wire, a bell, a push button and two C cells.
My light switches are similarly complicated.
My light switches are similarly complicated.
I know a guy who lives is a 1700's-era house. His is a bell, a pulley, and a string.
The problem is they've probably gone to the wrong house before and met an owner who got defensive.
As for availability, they are certainly very obtainable where I am in UK. Shops and Amazon etc have them.