But back to question: what calibrators works with Mac OS 9?
With all available software - GretagMacbeth (x-Rite) i1Pro
spectrophotometer. But not i1Pro OEM'ed for EFI (custom firmware).
About 1Pro2 I'm not sure. Most probably not, since it's too modern.
Also, depending on software, a whole bunch of colorimeters - various Spyders, i1Display etc, but don't waste your money on them, they are toys compared to i1Pro and might be either dead by now or deteriorated and will produce measurement errors.
I posted in 2018 about similar subject in this same forum. Here's an update re. software that I mentioned in that thread:
1. Serial# for Quato iColor Display 2.5.4 is in the SerialSeeker.
2. It turns out that Profile Maker 5.0 works in OS9 too! It just needs to be installed+patch applied on OSX and then moved over to OS9.
IIRC, it needs to be moved out of OSX package too. A copy could be traced down using usual methods