I got them from the lakes chain. I'll give the hint in that is not one of the isolated lakes, it's connected by the one of the canals or pipes.
There's a couple that aren't, for example Nimi. But I was on a main part of the plx. Not an obscure channel or back water.
I was told Nimi, Summit, and Springfield were considered part of PLX. If I'm wrong about that I'd sure love to know. Don't want to spread misinformation.