RE: Perko 500-10 strainer drain plug
Drain plug is not listed in Fisheries Supply catalog either. Tie rods, cover bolts, baskets, and gaskets for the 493 and 500 series are listed, but no drain plug. I'm guessing it may be a standard pipe thread, but that's just a guess. I'd try calling Fisheries 1-800-426-6930 and see if they have one on the shelf and can at least tell you what you need. This presumes your old one is lost in the bilge and can't be found? If you have the old one, try a plumbing store and look for a match.