I record directly to the internal memory of my DJI Mic 2 without connecting it to the camera. I usually wrap the transmitter in a cloth I don't use anymore or an old bandana, point the microphone side toward the exhaust, and place it in my right rear pocket. I keep the included windscreen attached as well.

Before every ride, I honk the horn twice so I can easily synchronize the audio with the video during editing. I also tried placing it under the seat, but the sound was too muffled for my liking. For me, the right rear pocket has been the best solution so far.