@deone Many cable manufacturers can build RCA Coax to BNC without the use of an adapter. I am a dealer for DH Labs and Cambridge Audio, and I know the DH Labs D-750 is one example of a cable that can be built to this configuration. I'm sure there are other manufacturers that do the same.
With digital cables, I highly suggest not using adapters as any voltage and impedance fluctuations can alter the quality of the signal and sound while also being a point of entry for noise and jitter.