You might try someplace like Coastal Farm and Ranch or Foster Feed to get actual stock tanks.

I have been thinking about this for a while and still may succumb to the idea. I haven't called around but you could try to find out who sells metal culverts to retail and then get them cut to size. They come in a variety of diameters. One of the ranch stores may be able to help you since a lot of farms and ranches have them under roads.

Thanks!

Try building one yourself! We built one in a day, and so far it's working out great.

Here is a link that might be useful: DIY Corrugated Metal Garden Planter

These are some I made with cheap roofing from Home Depot. I just cut to length, rolled them up and pop riveted them. these have no bottoms.

The round, corrugated style can also be made in a large diameter by joining several pieces of roofing at the seam using galvanized or stainless screws. I have one that is 7 feet in diameter that surrounds a giant fir stump in my yard. I filled it with dirt and planted a small maple. I used a different style of metal roofing in a medium brown to blend in with the surroundings.