I've had two direct from The British Library, Free on both occasions.

Contact

The British Library
Bibliographic Development
Boston Spa, Wetherby
West Yorkshire
LS23 7BQ
United Kingdom

Tel: + 44 (0) 1937 546548
Fax: + 44 (0) 1937 546586
Email: bd-info@bl.uk

Web Site http://www.bl.uk/bibliographic/isbn13.html

All the best

Jim Hancock