Years ago when doing my Phase I flight time, I used a very small voice recorder. I put the small microphone in my headset earcup. The recorder could be programmed for different recording modes; I used the voice activated feature to keep the (recorded) dead time to a minimum. After each flight, I would transcript the recordings into hard copy in the comfort of the FBO.
I purchased the recorder from one of the big box office supply stores. It was small enough to fit easily in my shirt pocket. I think in this mode the recording time was 36 hours.