Well, apparently there is a book that it is likely to be in:

STEVENS, Meic. I Adrodd yr Hanes: 51 o Ganeuon Meic Stevens gyda cherddoriaeth. Llanrwst: Gwasg Carreg Gwalch, 1993.

The local shop doesn't have it; if I'm up at the library end of town over the weekend, I'll see if there's a copy there.

sian