You asked for Herd Immunity as defined by R0, but the R0 term specifically refers to an

"Herd immunity" is a fancy way of describing the path of infection when r0 <1.
https://www.path.org/...urney-herd-immunity/

But

"herd" is subjective which is why you and I do not have to worry about AIDS even though there is no vaccine.

and

"immunity" is subjective which is why there is not a lot of concern for lack of vaccine for common cold.

The original question was "Do you have an example where we've reached herd immunity for a disease without a vaccine?"

This is a meaningless question for the points above. The fact that those that use this phrase cannot define it in objective terms should tip you off to this point.

If you phrase the question to "name a disease without a vaccine in which r0 <1" the answer is "almost all."