Hi Johnny,
I?ve used polyurethane to waterproof 550 paracord in the past on some projects and it stiffens up the cord pretty well in the process (but perhaps not as good as lariat rope). Maybe if you stiffen your cord with something like polyurethane, some of the suggested loops previously mentioned will hold their round shapes better and will work for you.
My vote is for something like the double fisherman. I?ve used this with paracord on tent tie-outs and they seem to hold a round shape pretty well (probably due to the number of turns in forming the knot a third of the way around holding the shape open).
Good luck.