Processing musical instrument output has shown the largest possible buffers to be necessary for recording audio on a raspberry pi.  The fragment size for ALSA was stepped up to 256 samples & the total fragments to 3 for realtime monitoring.  The mane need was to create a buffer of 30 minutes for writing to the SD card.

Helas, the 2 channel version needs a better clandestine microphone.  It has 2 electret condensers from digikey from 20 years ago.  These sounded marginally better than electret condensers from 30 years ago but nowhere close to a Zoom H2 from 15 years ago.  The Zoom handy recorders use very special electret condensers that sound more like studio microphones.  The trick seems to be holes in the back side.  The holes make them unidirectional but also give them a bass response normal microphones don't have.

There's no part number & nothing on the internets matches.  There is but 1 microphone which matches the dimensions & is unidirectional, the mighty CMI-5247TF-K.

https://www.digikey.com/en/products/detail/cui-devices/CMI-5247TF-K/1869988

It has 6 instead of 7 holes & doesn't claim as much bass.  The bass in the Zoom H2 might just be proximity effect.  The CMI was introduced in 2008, 1 year after the Zoom H2.  It might have been exclusively for the Zoom H2 or this type of microphone didn't exist before the Zoom H2.

There's is a standalone microphone capsule for the Zoom H5, H6, H8.  It costs as much as the entire H2 did & only has 2 microphones.  Despite all the fuss about stereo recording, the lion kingdom only ever needed it once.  In a clandestine mode, they may not sound as good because the back holes are going to be covered up & they won't have proximity effect.

Ross Guy showed some details about his setup.

It takes a long time for that guy to get set up  to record his bike rides.  The lion kingdom was surprised how painful it is despite much more expensive gear.  He's cabled into the bike rather than having a wearable recorder.  Of course, live streaming while recording is a new set of challenges.