I think I may have actually answered my own question. I'm in the process of slowly porting books over from the Zon to D2D, and I see that D2D has a POD production/distribution service. I have not figured out how to use it yet. It will generate a PDF of your ebook, presumably to use in the file upload of a print version, although I did download the PDF and it was woefully inadequate (of course.) Presumably I can use the same PDF I used for KDP Print (except with a new internal ISBN number) so I'll play with that.

Or not. I don't sell any significant number of paperbacks anyway, and I guess if someone really wants one, they know where to get it. At least for the time being.