It's not really off topic to discuss triple rows. Most zydeco players use both cajun accordions and triple rows. Some use piano accordions as well.
Most triple row players use accordions with 4 sets of reeds, in a LMMM configuration. Some use two sets of reeds, set to MM. But that wouldn't work for me. That low tuned reed makes all the difference in the world and I would really miss it. There are also 3 reed triple rows, set to LMM. I happen to have two of those. They are both Hohner Corona IIIR, one from the 60s and another of very recent build. They have 5 switches, and are tuned G-C-F. I don't gig on them, because I prefer F-Bb-Eb, which is probably the most common tuning for zydeco, followed closely by G-C-F. Other tunings are very rarely used, but you see them at time. E-A-D is likely the most common of these "other" tunings.
As for brands, in no particular order, there is Hohner, Gabbanelli, Dino Baffetti, Guerrini, and others I am not remembering off the top of my head.
My first triple row was a Guerrini, 4 reed, 9 switches, F-Bb-Eb. It has stood up to 30 years of hard use.
Later, I bought the 2 Hohner Corona accordions. They are both excellent, and I have to say that Hohner really outdid themselves on the recent remake of the IIIR. It is outstanding in all respects.
Many players used Gabbelli, particularly in the 90s. I think they are over priced, and not as high quality as they should be.
The Dino Baffetti brand seems to be the choice of most professional zydeco players for the last 10 to 20 years and for good reason. They are arguably the best. Very expensive, however.
Roland made a good reedless triple row - the FR-18. I bought one in 2011. It is actually the main triple row that I gig with for the last 5 years or so. It is lighter in weight than acoustic accordions, and it is much less expensive. Roland stopped making them, but you can still find them for sale. One really cool thing about the Roland is that you can change the key. I normally set it to F-Bb-Eb, but with the touch of a button (well, actually 2 buttons), I can change to any other key. I have one song where I change it to E-A-D, and a few other songs where I change it to C-G-Bb.
If you can find a Roland FR-18, that might be your best bet. They sold new for around $1800, so don't pay more than that. Somewhere in the $1000 to $1500 range might be good, but I don't know what they typically go for. This would be my first recommendation.
My second pick would be the newer Corona IIIR. This is the one with 5 switches. Don't confuse it with the regular Corona III, which has MMM configuration and no switches. I bought mine a couple years ago, used, for $1800. That seemed like a very fair price to me.
Another great thing about Roland is that they don't require any expensive maintenance or repairs, unlike acoustic accordions.
Thanks for taking the time to give me all that information! I had thought Hohner was making a Corona with LMM but couldn't find any information. I know the quality of both Guerrini and Dino Baffeti because I owned piano accordions from both manufacturers.
There is a Dino Baffeti dealer about two hours from me but for my first triple row I want to buy used.
I like your advice about the Roland. I haven't seen one for sale in a long while but I suppose if I search more seriously I could find one.
I would prefer a LMMM which is the setup of the pa Guerrini I owned. But ai am trying to get away from the weight of accordions with four sets of reeds except, of course, for the single rows I own.
Thanks again. I'll keep looking, be patient, and wait for something to show up. I no longer play in a zydeco band, wher I was playing piano accordion, so I am not in a rush. A three-row initially will be to satisfy my musical curiosity and give me another accordion-playing challenge.