It's not the same, but if you'd like to have a go at mainframe technologies you can do it with a Pi Zero:
https://www.rs-online.com/designspark/my-raspberry-pi-thinks...
Once you have the basic emulator setup working, check out the Turnkey system below. It's MVS 3.8 so not current Z/OS. If you google around for z/os ADCD, you might find an actual Z/OS CD to try next.