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.
