I recently purchased a Latin-Irish Gaelic Missal from a fellow I got in contact with from the Latin Mass Society of Ireland latinmassireland.org/
Cost me 60 Euros. It’s in the mail now, I’m eagerly awaiting its arrival.
Of course, that’s not Scot Gaelic… you’re not going to find one in print today. What you need to do is look into the history of what was printed back in 1962 and prior to that year. I found that the Irish Government published missals with Irish Gaelic; of course, the Irish government has always been very big on pouring money into the cause of the Irish Language. I do not know what bodies or entities might have had a concern for printing a scottish gaelic to latin missal…
Prior to ordering it, I was attempting to translate it on my own. My sources were the novus ordo missal in gaelic and a gaelic psalter I found on the Church of Ireland website ([edited by Moderator] it was the only psalter I could find in gaelic! haha, it was basically the same, at first I was confused, but then adjusted for the change in psalm numbers and found all the right things).