Although magnetic plugs are great, and I want them (and don't have them), for years on the farm we used the magnetic cow pills. For those of you unfamiliar with them, these are cigar shaped magnets, about three inches long and about half an inch in diameter that you feed to cows. Yes, really. Cows, you see, especially those at old farms, suck up nails, fence staples and odd bits of wire while browsing. Needless to say, with four stomachs, it makes them feel bad. Although I never got the nack, my father and grandfather were really good at telling when a cow needed the pill. Down it went, the cow was kept in the barn (we field fed our dairy herd) for a while, and eventually the pill and what seemed like a pound of metal crap came out. Not nice in the recovery phase, but that's dairy farming. Anyway, we also used these on the tractors and other machinery before fluid changes. About three or four operating hours before a fluid change, stick said magnet on the drain plug, apply some duct tape so it doesn't roll away, and when it is time to drain, one finds a nice collection of metal fuzz on the end of the plug if all is well. If not, one gets chucks and then trys to fit in a tear down in between all the other stuff that's going on that you don't have time for.
Anyway, I'm not sure how many of you have dairy farm supply places around, but the method is the same with a regular magnet. I'd suggest the rare earth magnets as they are getting cheap on line and come in coin sizes. Not as easy as magnetized plugs, but effective.