Turns out that there is at least one advantage of having constant plumbing problems – you often have the part you need. I had been noticing a leak under the kitchen sink. In checking it out, I found that the nut holding the drain in place was lose. As I tried to tighten it, the nut broke up in my hand.
Resigned to not having one of the dual kitchen sinks, I put a bucket under it and blocked it up. After dinner, we went on our walk and on the way back in, it occurred to me that I had a spare drain segment with a plastic nut. Installed the new nut and no more leak!