Microphone recommendation for recording acoustic guitar ?

Howdy y'all ... I play guitar, and like to sit on my screened-in back porch on beautiful summer evenings and play my acoustic. Recently I've begun to record my playing using the voice recorder on my phone ( I'm using a Note 2 with the Alliance ROM ). This approach works, but the resulting quality of recording is about what you'd expect from the built in mic. Are there suggestions / recommendations for an external mic you might be able to share? the only requirement I would have is that it be able to plug into my phone directly; in a perfect world it wouldn't require batteries or have an external power brick. Any help would be great, thanks!