Over the years I've made 3 hoods, for 3 different evaporators. All made using aluminum. 1 &2 were made using flashing, the third was made using sheets from a metals supplier. That was far heavier gauge aluminum and it really taxed my aluminum trim brake, but it finished well.
On my current pans which I ordered custom made by Thor in Quebec gave me a good price on my pans, but when I then asked about a SS hood they priced it a $1950 US. I said I'd make my own, but when I drove there to pick up the new pans they asked if I had made the hood yet, which I hadn't. I was waiting for the pans. Anyways, they asked if I was still interested in one, they had a demo unit the right size that had some minor damage. I looked at it, and the dent was very minor, so I asked how much, they sold it to me for $800, $1150 under the quote. I bought it. At this point I can't find the dent that saved me the money, and it has no new dents.
Maybe check around, somebody may have a 2x3 that has a dent. Being 2x3 means you can put almost any manufacturer's hood on.
If you get a local tin smith to make one using SS be sure it has gutters around the inside to catch condensation and a drain to send it to a bucket. A hood and it's stack catch lots of condensate. Under the stack you want a shallow funnel suspended from in the stack and a drain to the gutter.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.