Some authors reject that populism is even a terribly meaningful concept, but leaving aside that general rejection, for those who admit that populism is "a thing" and likewise admit that the far-right is definable, are there examples they give of groups or parties that are far-right but not populist? And if so, under what definitions of these terms?
Any question like this depends on the implied definitions of "right-wing" and "populist". Populism is normally seen in contrast to "Elitism", and so we are looking for groups that espouse the xenophobic, ultranationalist views of the far right, but support, at least in principle, rule by an elite.
One way this can happen is if the "elite" is identified with a minority ethnic group. For example in South Africa there are groups such as the Afrikaner Weerstandsbeweging, which espouse "white supremacy" over the majority in South Africa. For them, the white "race" is an elite that should rule over others. This group is undoubtably far-right, and probably not populist by most definitions.
Another example would be Theocratic groups that desire domination led by an elite of religous leaders. Islamic State (ISIS/ISIL/DAESH) would seem to have many of the xenophobic aspects of the far-right, combined with the desire to establish a Caliphate with an elite ruling Caliph. This group is undoubtedly not populist, and probably far-right by most definitions.
There are other groups that, for example seek to establish absolute divine rule by a king, for example in Japan, there are groups that want to get rid of democracy and make the Emperor the sole ruler of Japan (even though the Emperor has not expressed any desire for such a role). Again you see here a combination of ultranationalism and elitism.