I have been using a similar wrench - what I grew up calling a monkey wrench - for the last few years. It is heavier than the one pictured and has wooden handles. The jaws are slightly "sprung" from heavy use so they are not parallel and they fit a breechplug almost perfectly. You can pick them up at flea markets and yard sales around here for a few dollars.
I used to pad the jaws with scraps of aluminum flashing, but don't bother anymore.
El, I may have a spare in one of my junk boxes, would you like me to look? BTW, where in North Carolina are you? The company I work for does consulting specializing in casinos, and I flew into Asheville and drove to Harrah's Cherokee a few weeks ago. Beautiful country, reminds me of the eastern panhandle of West Virginia where my father grew up.
Dale H