Here's another version of it which I found in a book, 'Eilean Fraoich: Lewis Gaelic Songs and melodies' which I hope is still in print, the copy I have was published in 1982 by an Comunn Gaidhealach Leodhais (no author/editor credited)

Mo nigh'n donn ho gu
Hi ri ri hu lo
Mo nigh'n donn ho gu.

Mo nigh'n donn a' chuil bhain
'Se do ghradh rinn mo leon.

Mo nigh'n donn a' chuil chais
Deud mar chailc 's gruaidh mar ros.

Mo nigh'n donn a' chuil reidh
Bha mi'n deidh air do thoir.

Mo nigh'n donn a choisinn geall
Far na champaich na seoid.

'S bithidh mo lamh-sa 'nad laimh
'S neo-ar-thaing do n' tha beo.

'S bithidh mo lamh mu d' chul ban
Ged a ghearrt i mu'n dorn.

'S bheirinn oidhch' air son oidhch'
Air son caoimhneas do bheoil.

'S theid mi null air a' bheinn
Far 'm beil loinn nan ban og.

'S bithidh mi comhl' ri bean na bainns'
'S bithidh mi'n ceann a' bhuird mhoir.


I'll attempt a translation, be warned my Gaelic is a bit rusty, maybe someone more fluent could correct any mistakes...

My brown lass ho gu
Hi ri ri hu lo
My brown lass ho gu.

My brown lass of the fair hair
It's your love that has wounded me.

My brown lass of the neat hair
Teeth (as white as) chalk and cheeks like the rose.

My brown lass of the smooth hair
I had pursued you.

My brown lass of the little white foot
Where the warriors were encamped.

And my hand will be in your hand
And will not be pulled away by a living soul.

And my hand will will be about your fair hair
Even though it is shorn about my fist.

And I will carry it night after night For kindness of the mouth.

And I will go across the mountain
Where there is a choice of young women.

And I will be together with the bride
And I will be at the head of a big table.


Phew!
This doesn't seem to be the same song as the one Malcolm gives above although it has one or two similar verses (floating verses?) but hopefully one of these is the one you're looking for.