Sorry but it can't be done.
UTU was a lightweight tool that, under the covers, talked directly to Prime LMS's Sybase SQL Anywhere database. Similarly the Prime LMS Widget did as well.
Prime Infrastructure uses an entirely different Oracle database and is thus not compatible with UTU.
There's currently no equivalent tool for the desktop and I've not heard of plans to introduce one. :(
There was the Cisco Prime iOS app that offers a "clients and users" view. It may be of use to you - I haven't had the chance to try it on a live system.
It appears Cisco has abandoned this app though since I can't find it on the app store anymore after looking just now. I do have it on my iPhone. :)
