Lighting

I have an outer orbit fixture that I want to hang from the wall or ceiling. My ultimate dream would be a retractable cable hanging mount of some type so that I could raise the fixture when I need to get into the tank. The tank is thirty inches deep so when I need to get near the bottom I have to almost lay across the top of the tank to reach. Anyone seen a setup or know where I could get something like this? I remember in my fathers house we used to have a dining room light that could be raised ...