Here it is: http://userscripts.org/scripts/show/8432
A very minor tweak allows me to use it for Boston.
http://www.bookburro.org/
Finds item at both online stores and numerous libraries, including my local ones.
For the Metro-Boston library, it is
var libraryUrlPattern = 'http://catalog.mbln.org/ipac20/ipac.jsp?index=.BN&term='
*-To edit the script after installation, open it using the Greasemonkey icon in your browser. Click on 'Manage scripts' to open scripts in an editor.
Here it is: http://userscripts.org/scripts/show/8432
A very minor tweak allows me to use it for Boston.