One of the kids sleds lacked anything to drag it around with, and one of the others had a too short a rope, so quickly made these. The handle is designed to be easily printable and strong.
Print these and use together with 3 mm polyester rope. Cut the rope to a good length (around two meters), and torch the ends briefly. Thread the rope through the hole and make two knots on top of each other right at the very end (top of the handle/larger hole). Pull the rope back into the handle.
I printed these with 30% in-fill, and they feel very sturdy.
Update: They ARE very sturdy. We spent a day on the mountain. I have dragged kids in the sleds up steep slopes. The kids have repeatedly been running them over with the sleds. These handles are tanks.