I'm not sure I'm understanding what exactly you want, but you could also use a spectrum analyzer and determne the frequency of the fundamental spur.
Or is it that you're wanting a chip or a circuit that determines the frequency?
I know there's a gizmo (which I've never used nor know anything about) called the FFT (Fast Fourier Transform) where, given an input signal, the output is the FFT, the frequency content of the signal. Moreover, I'd recommend looking into finding FFT IC's, as I know they exist, perhaps only as processors.
(Granted, I know about the Fourier Transform, which may be the same as finding a Fourier Series, but I know nothing about the FFT beyond what I've said.)
P.S. To anyone reading, if you know more about the FFT, please speak up, as I'd like to know more about it. For example, is it an abridged Fourier Series of a signal/waveform?