Can I get some advice about 94 4Runner oil pan drain plug issues?

My 94 4R with V6 and 218K miles is in pretty good shape, but has some minor oil leaks. The bottom of the pan is always wet with oil, but some of it may be from leaks from above. My concern is that some of the leaking may be from around the drain plug. I think this is the original plug, but the plug contact with the pan is steel-to-steel without any kind of gasket. I'm afraid to add any kind of gasket because of the limited number of threads on the plug. Where can I get a plug with a longer threaded section and a good gasket, so that I can eliminate the possibility that some leaking is going on? Or should I just assume that the steel-to-steel contact is doing the job?