HDMI port to VGA display

Hi:

I just bought the OWC Thunderbolt 2 dock and am setting it up with my brand new awesome MBP13. I would like to use the MBP13 and the dock with an old but still very functional Cinema HD Display running firmware version 7.36. The external display runs great if I use a Thunderbolt to VGA adaptor from the dock, but that uses up my solitary outgoing Thunderbolt port on the dock and I would like to use this Thunderbolt port for external hard drives. There is an HDMI port on the back of the dock, but I cannot find a VGA to HDMI adapter at Apple's store (but perhaps I am just looking in the wrong place). Can anyone tell me how to use the HDMI port on my new dock to connect to my external VGA Cinema HD Display?

Thank you!