PlantAnt shows availability of P. mesocarpa at a few Homestead nurseries...Everything Green lists 7g and 25G; Greendale Nursery shows 10g, and Botanics Wholesale with huge plants (65g, 15'-17' p.h.). You might also email Jeff Marcus at Floribunda Palms in Hawai'i, he doesn't generally put this on his availability lists anymore but he may still have some, it never hurts to ask. He would probably be the best source for mail-order if you can't drive over to the Miami/Homestead area to pick one up. You might also query Jeff Searle (who is still somewhat active on this forum), who has closed his nursery but may sometimes still sell material, or perhaps he can help you source one. I bought one from him when I lived in the Keys, though that was when Searle Bros. was still very much in business. P. henryana may be a difficult species to find just because it doesn't have a good reputation for cold-hardiness. I also remember it didn't seem happy, presumably due to our calcium carbonate in the Keys, as it was pretty chlorotic in my garden (perhaps just not rainy enough there to mitigate the high pH) and finally just faded away. Of those spectacular entire-leaf palms, I found Verschaffeltia and Phoenicophorium far easier to cultivate there. Best of luck in finding what you're looking for, I'm sure there are some out there...