Perhaps you've already tried this, but I occasionally find success by individually searching the names of all the relevant credited art department crew. It's tedious, as many of them will be dead-ends, but I'd say maybe 1 in 20 generally turns out to have a decent personal website with a listed contact. Those who work in graphic design / 2d illustration as opposed to 3d sculpture / fabrication tend to be better bets, so the concept art route may be more fruitful. I also often experience better luck with those further down the totem pole who have a need to actively promote their skills, so don't discount the juniors / assistants / trainees.
Even if the crew member doesn't appear to have worked on this particular prop, an email inquiring whether they happen to know who was responsible for it (ideally including a bit of genuine praise for whatever they did contribute) may get you a lead. Just a few weeks ago, I tracked down the fabricator of a particular helmet who turned out to be entirely uncredited, thanks to contacting a credited costume design assistant who remembered the name!
Also, if you strike out with IMDb, it may be worth giving the actual credits sequence a quick skim, as not every name gets entered online.
