OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
Le nouveau Dico : Français-Gallois, Gallois-Français = Y geiriadur newydd Ffrangeg-Cymraeg, Cymraeg-Ffrangeg. ISBN 9781845215408. Published by CAA in 2014. Publication and catalogue information, links to buy online and reader comments.