If you are looking for a water heater burner, the best place to find one is at a metal scrap yard. A lot of them have a drop off area that people can just drop off there metal junk for free 24/7 somewhere outside the yard. I just stopped by there in the morning before the yard opened and after the second attempt I found the one I wanted.
You need an older water heater as the newer ones from the early 70's on had the orifice mounted under the burner and the burner itself is tin.
The older version like in my pictures have the orifice in the mounting plate that goes into the burner and the burner itself is cast iron so you can crank the heat as high as you want and nothing will hurt.
I made the extension on the gas hookup purposely long so at a glance I can tell which one is the converted one and which ones I can take with me camping, lol.