Or else, is it still possible to buy them somewhere?
This blog might be what you are looking for:
A few are being sold on GOG: https://www.gog.com/game/the_zork_anthology
I believe that’s the only licensed seller at this time. Unless you have a really old iOS device, in which case the (32-bit) “Lost Treasures” app might still be visible in the iOS app store.
The BBC is still hosting The Hitchhiker’s Guide to the Galaxy.
I once acquired a semi-complete collection on diskette. It was called The Lost Treasured of Infocom (I/II). I bought it again–I believe in the late 90s–in a CD-ROM rerelease.
archive.org is also hosting the Classic Text Adventure Masterpieces of Infocom here: