The copper coil heat exchanger was a little too wide for any of my containers, so I built a soft tank from 10′ of mylar coated bubble wrap and a garbage bag.. It’s well insulated and leak tight. I’m going float Styrofoam balls on the surface for added insulation. I got this idea from Tom Gocze almost 30 years ago. He still sells them at the link below. So far I the tank hasn’t exceeded 140F, so I haven’t really tested the high temp limits.