Might try
https://www.hummer-parts.com/oe_parts_catalog.html
Fill in the year, make and model of your truck then look under "Instrument Panel" then "Instrument Panel" in the drop down and then look at "Power Outlet Retainer", item number 18 on the 03-07 model years. There will also be the option of "View Illustration" so you can see all the parts.
Hope it helps, Ed