I tried an iPhone headset, not that great. Had best results so far (shown in the video I uploaded) with the use of the internal mic and my normal in ear Sennheiser earphones. Whatever you use has to be a line level input so if you want to use a dynamic mic you’ll have to run it through a preamp first. Remeber OP-1 Field supports some USB audio devices, so consider using your Zoom H4 since you have it but plug your dynamic mic into it instead.
I second the Tula mic with a variety of sources for the op1f. Direct vocals, guitars, sampling, vocoder, etc. And their support team is great too.
It’s a sensible little mic - not at all on par with TE’s proposals. But as a go-to cheaper alternative, it’s as good as it gets.