I went to a local plumbing/electrical supply store and got copper for about half of HD or Lowes prices. The small diameter copper wire I used to hold everything together came from some old fluorescent lighting fixtures. I stripped off the insulation and the bare wire was perfect for what I needed.
Here's some photos of the one I built. I got the general idea of the "ribcage" design from a discussion here on HBT, and modified it to suit my needs. It works really well, and was easier to build than I thought it would be.
The top tube makes a nice handle for getting it into and out of the kettle. The two T joints on the top tube are structural only, meaning I filed out the inside of the T's so the input/output pipes go straight through them. When it's all soldered and wired together it is a nice rigid structure.
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