Can anyone help me figure out the base size of this light socket?

I have one light fixture in my new house that has this light fixture. I know it's a plug in CFL, but can't seem to find the right bulb. Locally I've only been able to find GX23 base plug in CFL's, but those don't fit. Could someone help me figure out what light bulb I should order? Picture of light socket: http://i.imgur.com/sz5fDec.jpg

Submitted November 30, 2014 at 04:55AM by panorama_change http://www.reddit.com/r/DIY/comments/2nspq7/can_anyone_help_me_figure_out_the_base_size_of/