Plateau clarinets used to be hard to come by, but now there are several companies providing good alternatives for anyone wanting a closed-hole clarinet.
Plateau clarinets were first marketed for young students with small hands, but in more recent years, senior citizens with arthritic fingers (especially those in New Horizon bands) have been snapping up the ones that were previously available, especially the Normandy plateau clarinets.
Our friend Melinda showed me her new Rheuben Allen-Hunter Custom Plateau Clarinet (pictured here). I had a brief chance to play Melinda's clarinet, and I liked it very much. At $745, this seems to be the most reasonable new plateau clarinet that I've found. It is a modified Chinese clarinet.
Melinda's need for a plateau clarinet is due to her right hand second finger loosing the first joint due to cancer. That is not holding her back from playing clarinet, flute, and piano.
This looks to be trouble-free keywork. I don't see any adjustment screws, and I forgot to check for that when I was holding the horn.
I have also found the Hansen Plateau clarinet, made in England.
I am impressed by the description and pictures.
Two other fine models are offered by MRW Artisan Instruments in Florida.