I needed a holder for my 9v battery dummy thingy. It was originally intended for a rode mic which I had to modify to open a hole in the back.
It was made for my hard 9v adapter and probably doesn't work with flexible connectors. I'll attach some pics to see if it helps somebody else.
It has some niceties, like a slim profile so you can grab it, a channel for cables on the side and some grip for the connector. Might be a little large, it fits tight but you can always sand it for better fit.