Depends on what your are recording, how you run, what you are willing to spend, etc.
I'm not up on all the options into phones. But here are a few examples of quite different options at either end of the range. Some have been mentioned previously in the thread:
Shure MV88 > phone- low cost, all in one, attaches directly to phone.
One of the binaural recording sets like the Sennheiser Ambeo, or the Roland mic earbuds, or (there is/was another one) > phone
DPA microphone pair > DPA d:vice > phone- higher cost, choice of any DPA microphones, most stealthy
Any microphone pair > Sonosax SX-M2D2 > phone- expensive, arguably as good as it gets