[1] https://en.m.wikipedia.org/wiki/N%25C7%2583xau_%C7%82Toma
https://en.wikipedia.org/wiki/Click_consonant
https://www.compart.com/en/unicode/category/Lo
https://stackoverflow.com/a/4843363
I was extremely puzzled until I realized you meant a click sound, not a clock sound. Adding to my confusion, the vintage IBM 1401 computer uses ǂ as a record mark character.
https://en.wikipedia.org/wiki/Click_consonant
https://www.compart.com/en/unicode/category/Lo
https://stackoverflow.com/a/4843363