Go to the LEME (Lake Erie Maple Expo) this fall or the Jan Maple conference in Syracuse in Jan. Either will have what you are looking for and likely at the best prices of the year.
I bought a bunch of 26.5 gal SS barrels from the one in Syracuse. The vendors had sizes from 10 gal thru 40 or even 55 gal. Don't rune out the beer keg shape. There are new ones that look like a beer keg but that are designed for maple syrup, I think they are 15 or 16 gal and are new stock, not re-purposed. I also have one of those. Also, your State association might from time to time offer ss barrels, I also have 4 @ 16 gal ea. that were at one time sold by the New York State Maple Producers Association as a one time deal.
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.