Where can I get a high-quality ADC (audio digitizer) for Arduino?
You are going to need a bigger board. 

(96000000 samples/second) * (32 bits / sample) ~= 3 Gigabits/second

A poor little Arduino Uno only runs at 20MHz and can process 8 bits bytes at a time, so even if it could somehow read and store a byte every cycle, it would still be orders of magnitude too slow for your purposes. 

While I guess is might be possible to build a shield with an ultra high speed ADC and on board memory to directly store the captures samples to, you probably would bother making it since the Arduino would struggle to do anything useful with the captured data even after the fact. 

The highest quality audio recording shield for Arduino I've seen is a modified Wav Shield that can record 8-bit mono files at 44,100 samples per second using the waverp library.