You may need to tell us exactly what you want to do with this emulator, so we can suggest alternatives. Because indeed, true ICE for Z80 will be expensive, or hard to find, or you may run into very old, unsupported, maybe non-functional equipment.
Yes, as suggested before, maybe a pure software emulation would work in your case?
If not, what do you need to inspect on a hardware level? Maybe a simple board with a real Z80 would do, if you just need access to external signals.
It could otherwise be implemented in some FPGA, there are open-source Z80 cores out there (like the T80), that would give you the most flexibility in terms of what you want to do, but extra work which could become a rabbit hole.