I don't think so if you want them in a container like a box (which I certainly would). Especially on the way back - even a few days made a lot of difference in how strong and adventurous they are.I wondered if my body heat would be enough to keep them warm??
I used a couple of squarish shaped juice bottle - maybe a quart or two liter size. I put very, very hot water in them wrapped them in a couple of thin dish towels and wrapped that in press and seal plastic wrap (because I wanted my towels back unstained). And wrapped that in rags. I took layers of rags off at each stop as they cooled. They stayed warm enough for four hours. I had to refill them a couple of times on my much longer leg.
Rice bags would also work but water holds heat longer.
I was using a wool hen, which I think can be warm enough without the water bottles but I jerry rigged the wool hen until I got home. It was a little short of enough wool strips. Also, they still needed a little help going into it and It was just them and me on the road.