You can get a pre-compiled version of sudo for AIX at

IBM AIX Toolbox Download Page - Alphabetical Listing

You install with "rpm -i sudo*rpm"

(If you don't have rpm.rte installed on your OS you will need that first to install the sudo rpm.)

Now my memory is a little fuzzy but the following should work:

Enter "visudo" and add the line:

username hostname=/usr/bin/mksysb

:wq to write and quit visudo

Now the user would enter the command "sudo mksysb" and it will prompt for the users password and log what has happened in the syslog.