I have a lotus that I kept for two years in a large container, not in the pond. The first year, I dragged the whole pot into the shed, which gets cold, but which keeps the frost off. The next year, I merely covered the pot with painter's plastic, the kind you place on the floor when you're painting to catch the drips. I used the thicker plastic, not the thinnest they have, and since it was large enough, I folded it for added thickness. I erected a frame of some kind over the top so that the snow and rainwater would not puddle. A suggestion would be the wire basket that hold the coco fiber in some hanging baskets, or something that can tepee over it. On warm days, I opened it up to keep the heat from building too much, but my lotus did very well and two years later is now in the pond and blooming every spring. I added water as needed to keep it moist.

I actually overwinter my tropical water lilies in this fashion too, by building a lean-to over the large pots that I place them in, and covering it with plastic. I also place a small aquarium heater in the pots for the lilies, but I did not do this with the lotus. I have never lost a tropical lily by wintering them in this way.