Strain Relief

It turned that I needed a 12VDC to 3VDC converter.  I have that now and the combination of cigarette lighter plug and converter is giving me the desired 3VDC.  Ideally, I would like the converter box and the leads to the plug wires to be contained and with some sort of strain relief to prevent stupidly pulling the leads on the converter loose from the plug or the wiring to which it connects.  The converter is 2" x 1" x1", with little open end holes for screwing it down.  If Radio Shack still existed, they would have something in which to confine it, and likely something to provide strain relief.  But what am I looking for online?

Thanks all.  Project box.  Just need to drill a hole in each end for the wiring, and put a serious knot in the wires to prevent them from going through the holes.