And they are rimfire to boot.
I don't know that any .44 Henry has been made since before WWII, maybe a lot before WW II.
You could no doubt get one or a few from a cartridge collector for display but it would be a huge expense to get shooting quantities, even if they were still live.
Uberti made a few .44 Henry rimfire repros to be sold as display pieces in repressive regimes where their .44 - 40s could not go. Possible because ammunition is all but unavailable.