Cobalt also has launched the complimentary 9927-2StoH 3G/HD/SD dual-channel openGear SDI-To-HDMI converter card that incorporates all the same features as the 9926 modules. Both the 9926 series and ...

Even a simple "map the HDMI pins to dual Cat5e/6" adapter like this one still mentions that it's powered (though in this case by pin 18 of the HDMI jack), so I'm not sure it'd do what you want.