How do you make the 'select' dropdown when choosing a different list larger?

I need to change the width of the dropdown in the select which list to be wider...

I see that if I change the style:
.cbUserListChanger.text-right {
width: 250px !important;
}

however, now I would need the listchanger to be a little more to the left...

What can I do to make this adjustment?

A sample page is this:
polisci.rutgers.edu/index.php?option=com_comprofiler&view=userslist&Itemid=300291&limitstart=0&searchmode=0&search=&cbsecuritym3=cbm_0f4d2524_11f51d56_aa60e4ed6bbc9ff237a5cd765776505c&listid=25&name=&username=

thanks,
Laura