They're not available for sale, but you can find them all as clickable epubs. (Any device that can run a Z-machine can run an epub reader just as easily.)
Any modern device will run both, but Infocom's Z-machine ran on old 8-bit home computers. Even if you ignore EPUB's image support (which includes the complicated SVG format), EPUB is zipped XHTML+CSS. I'd be very surprised if you could fit a parser and renderer for all that in the limited RAM they had available.
V3 games ran on 8 bit computers, but v5 games (most of modern ones) only run well under a 16 bit one.
As for epubs, netbsd runs on Amiga and Classic Mac, and if lynx and unzip work, so do epub files with a crappy script.
It's 2020 and an RPI or an ESP32 are dirt cheap, and you can get a 486 machine even for free.
I suppose an epub would be pretty easy to convert (on a modern machine) into something like ZIL for ZILF. Good thinking.