as far as my knowledge of the topic goes, there is no Celtic equivalent of the Nornir.
Among the Celts in the Roman provinces Germania Superior and Germania Inferior there was a triad of female deities commonly known as 'mothers' or 'matronae', who were later adopted into the Roman pantheon. As far as we can say these deities were not associated in any respect with fate, however. They are sometimes depicted with what could be fruits of the field, and usually are of the same age. It is generally assumed that they are earth, harvest or tribal deities (taking care of the wellbeing of the tribe). In that they may more resemble the Germanic Disir which is a group term for Germanic female deities, female ancestors and nature spirits.
The Germanic contemporaries of the Celts obviously had very detailed and complex ideas of fate which are usually summarized with the term Wyrd. Of how the continental Celts saw fate, not much is known. Maybe they had a less detailed... or different system and therefore no need for deities/spirits personificating fate?
I wish to learn the things that are
and understand their nature
and to know God.
(Corpus Hermeticum I,3)