OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
U2 TAG bioleg (BY4 a BY5) : llawlyfr myfyriwr : i'w addysgu o haf 2008 by Gareth Rowlands. ISBN 9781860856556. Published by CBAC in 2008. Publication and catalogue information, links to buy online and reader comments.