I am using 9.7 and it is available. You may want to open the DB2 LUW InfoCenter webpage doc for version 9.1 (V9) and search to see if you can find it. It might not be availble in 9.1.
If you want to try and copy it from a 9.7 release (probably in the $HOME/sqllib/bin directory) you could download a trial version of DB2 9.7 and get it from there, but no guarantee that it work if you try to run it in 9.1.
BTW, DB2 9.1 LUW will no longer be supported by IBM after Apr 30, 2012 (except under special extended support contract), so maybe time to upgrade to 9.7.