Well I checked out Kirk’s site, and found out that he has a DVD to go along with the old 4 disc CD-ROM sets:

In the 20 years since the release of the CSRG CD-ROM Set (1998-2018) I have continued collecting old software which I have put together in two historic collections. The first is various historic UNIX distributions not from Berkeley. The second is programs and other operating systems that shipped on or influenced BSD. The distribution is contained on a single DVD that contains all the original content from the original 4-CD-ROM distribution, these two collections of historic software, and a copy of John Baldwin's conversion of the SCCS database contained on the original disk4 to a Subversion repository. Unlike most write-once technology which remains readable for less than ten years, this DVD is written using M-Disc technology which should last for centuries. The price for the DVD is $149.00.

I know the $150 USD may sound pricy but the historic2 archive does contain a couple additional copies of Mach!

And a bunch of other stuff in there as well, it’s gigabytes of stuff to go through.