First, the good news -- I received an answer from a fella on the Daltaí na Gaeilge Discussion Board ( click here). Below is his original message:

Friday, June 2, 2000 - 05:55 pm:

A Bhean Chlainne Dhabhóic,

Is éard atá uait, bunleagan, nó athleagan, an amhráin 'Seán Ó Duibhir an Ghleanna' faoina ainm coiteann. Tá scéal an ainm agus an amhráin ríofa ag Tomás Ó Concheanainn, NUA-DHUANAIRE III a d'fhoilsigh Institiúid Ard-Léinn Átha Cliath sa mbliain 1981. Tá 112 líne sa leagan atá curtha i gcló ag an Uasal Ó Concheanainn. Luann sé Béaloideas uimhir 11 mar fhoinse. Luann sé chomh maith 'Amhráin Chlainne Gaedheal' Thomáis Uí Mháille. (- mairg an té nach bhfuil a chuid leabhar in aice láimhe -)

Tá an-duifear idir leagan an Nua-Dhuanaire thuas agus leagan an dá leabhar seo a leanas.

Ceolta Gael II, Ó Baoill, Mánus 1986 : dhá bhéarsa de 'Seán Ó Duibhir an Ghleanna'

Filidheacht na nGaedheal, Ó Canainn, Pádraig 1940, lch. 39 : ceithre bhéarsa de 'Seán Ó Duibhir an Ghleanna'

Beir bua is croch suas é!

Seosamh Mac Muirí

To sum up what Seosamh says (in English):

The song "Éistigh Liomsa Sealad" is a version of the song "Seán Ó Duibhir an Ghleanna", which is cited in the Tomás Ó Concheanainn's book "Nua-Dhuanaire III", published by Institiúid Ard-Léinn Átha Cliath in 1981. Ó Concheanainn also cites 'Amhráin Chlainne Gaedheal'. There's a great difference between the version of "Seán Ó Duibhir" in the book Nua-Dhuanaire and the versions in the books Ceolta Gael, and Filidheacht na nGaedheal.

The versions that we have on the Mudcat (in English and Irish // words and tunes) can be found in the following threads and, unfortunately, are not the version we're looking for:

SEAN O'DUIBHIR A GHLEANNA

Sean O Duibhir an Gleanna (Sean O'Dwyer)

after aughrim's great disaster

Lyr Req Wild Geese

I did manage to find the first verse of "ÉISTIGH LIOMSA SEALAD" in Tomás Ó Canainn's book Traditional Music in Ireland:

Eistidh liomsa sealad go neósfad díbh cé cailleadh
Gurab é Seán Ó Duibhir a' Ghleanna is gan trácht ar a ghéim
Go bhfuil a ghadhair, sa choin, sa chapaill go domhain fé chré dá gcartadh
Is nárbh fhios cár ghaibh an t-anam bhí in árus a chléibh.

Listen to me a while till I tell you who had died
John O'Dwyer of the glen, no more talk of his game,
His dogs and hounds and horses thrown deep beneath the clay,
And we don't know where the soul's gone from the haven of his breast.

The bad news is that I can't find the other verses of this version of the song. So, I guess we're still looking.

Keep your fingers crossed we can come up with it, Áine