Is it possible to authenticate ISE TACACS using Google Authenticator

[CCC3]

ISE is using 3.2 Patch 5.

I'm doing TACACS authentication through ISE
I want to do 2FA authentication using OTP.

DUO confirmed that it is possible, but I understand that it costs extra.

So I'm looking into whether there's any other way.

Among them, I wonder if Google Authenticator can support that feature.

And if there is any other way, please let me know.

[ahollifield]

What mechanism does Google Authenticator have to integrate with ISE?  Does it support RADIUS Proxy?  It certainly has no native local integration like DUO.