Nothing like MacKivigan is listed in G F Black's
Surnames of Scotland so it does look as if it's an Irish rather than a Scottish surname.
The best lead i've found is the variatons of McIver spellings, such as McIvey and McKiver.
I am very sceptical about that.
MacIver and its variants, according to Black, is a mixed Gaelic and Norse name meaning 'son of Ivar'. None of its recorded variants omits the 'r' or has an additional string of letters attached.
There is a Scottish surname 'MacGavin' which means (not surprisingly) 'son of Gavin'. If McKivigan is a variant of a simpler name, surely MacGavin is a more likely base name than MacIver? Though you still have to account for the '-igan' tacked on to the end of the name.
I think the origin of the name is far more likely to lie in Ireland than in Scotland, and therefore that McKivigan is not specifically associated with any Scottish clan.
If you are looking for a tartan the place to go is
https://www.tartanregister.gov.uk/Bear in mind that the clans were a social phenomenon of the Highlands, not the Lowlands, and that many common Scots surnames (Smith, Brown, Wilson, Reid, Young, Black, Clark, Watson, Wood, Jones, Gray, Johns(t)on(e), Hill, Wright etc) do not belong to any Highland clan, despite what the Brigadoon industry would have you believe.
Also that tartans as known today are largely a nineteenth-century invention.
If you want to wear tartan, just pick one you like and get on with it. There is no tartan police, and no-one will bat an eyelid if you turn up in a tartan belonging to a random clan. If you are worried about that, there are plenty of district tartans to choose from.