You can buy a vogelzang barrel stove kit. Easy to build. The best option is to find an old Sotz brand round door kit. Much superior to the cast Vz kit. I made a couple with salvaged incinerator doors also. Here is the sotz I built last year from a cutdown 15 gal drum.

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I have a couple of sotz 6" chimney flanges for the 35-55 gal drums if you need one.........Don