I finally got around to putting this together. I used 3/4" SS from amazon and one of the 800w heaters. I ordered two heaters, the first I was refunded because it never came. The second one arrived on time alongside the original order.
Both are supposed to be the same thickness but they are slightly different. I tried a 3/8" compression fitting but the nut is too large. I had to drill the inside of the fitting to get the element in. I'm going to try a smaller fitting and drill it out.
For what it's worth I brewed a batch with it and it worked great. I used silicone to seal the end but that didn't work too well. I didn't see any signs of scorching when I cleaned it. I ran it with a PID.