Purer forms than NI200 of many metals are readily available.
NI200 doesn't contain chromium (hexavalent chromium isn't relevant to vaping, unless you're melting your coils) or aluminum, but that doesn't really help anyone with a nickel allergy.
There's no perfect solution.
Waiting patiently for Dr. F.
Are people with Nickel Allergies effected by Ni200 coils?