OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
Cynulliad Cenedlaethol Cymru a chnydau GM : pum cam y mae'n rhaid i'r Cynulliad eu cymryd i gadw Cymru'n rhydd o GM. Published by Cyfeillion y Ddaear Cymru in 2002. Publication and catalogue information, links to buy online and reader comments.