I think the idea of duct tape is not fixing the root issue. I'm more worried about the conductors not making a large enough grip. The plug moving around in the socket is secondary.
Or, better yet, get a better power cord. Power cords make a big difference sonically and high quality power cords have very tight fittings.
Would rather make my own than ever buy one pre-made. DIY cables is part of how I enjoy my hobby so if I give that up, I might as well stop listening to music. :)