Some good options are:
Working With Words: A Handbook for Media Writers and Editors by Brian S. Brooks
When Words Collide: A Media Writer's Guide to Grammar and Style by Lauren Kessler & Duncan McDonald
Grammar for Journalists by E. L. Callihan (out of print, but you could probably find it used)
Some links to online book stores:abebooks: http://www.abebooks.com/
half.com by ebay http://www.half.ebay.com/
List of Bookstores on the Web http://www.scaruffi.com/fiction/booksell.html
