I don't know if you guys have "Lululemons" in the States, they're just stores with TONS of workout clothes. I adore going there because they have every kind of yoga/track/workout pant in existence.
I too have the dreaded thighs-touching dilemma, and as a result of that I tend to wear stretchy black yoga pants that shield my legs from friction. The great thing about finding a store that specializes in workout gear is that they normally have a ton of different STYLES, so I was able to find a stretchy black capri workout pant with a flare in the leg to avoid (as someone else so entertainingly called it--) "carrot leg".
Of course, if you're just chilling at home and aren't too worried about aesthetics, you can really find any kind of functional pair of PJ pants or stretchy capris at somewhere like Old Navy or Walmart like others have suggested.
Good luck!!