Personally, I just use a 4' length of ½" PVC as a pipette. I leave the sample cup on deck and just plunge the pipe in with my thumb capping it, let go, let it fill, cap it, and pull it out and let it drain into the cup. But that still involves some kneeling to set the cup down.
I can't find it now, but somebody rigged up a water bottle and a PVC pipe with some bungie cords and made a sampler that way.
Seems if you attach the sample bottle at an angle, you can push it under upside down so there's an air bubble trapped inside, then turn it over at the right depth and let it fill up. Then just pull it out. You can do the whole thing standing up.