The file is available relative to the stylesheet you are downloading.  This can be a little confusing so here is the direct url:
Corey Keith / [log in to unmask]
Digital Project Coordinator
The Library of Congress
Phone: 202-707-7196 / Fax: 202-707-0115

>>> [log in to unmask] 2/17/2004 11:32:01 AM >>>
I'm trying to run marc4j in its xslt mode to get MODS records, but the
marc21-slim to mods3 includes a file called MARC21slimUtils.xsl that I
can't find anywhere on the LC site. Help! and Thanks.
Karen Coyle
Digital Library Specialist
Ph: 510-540-7596 Fax: 510-848-3913