This brief article is based upon my own personal experience with the DPA 4099 CORE mic.
I am not paid for my opinion on this product, nor has it been supplied to me for free. This is not an advertisement. I am sharing what I know as a courtesy to you, the reader.
When I encounter a quality product and am able to successfully demonstrate its value, I often become enthusiastic. Please don't mistake my genuine enthusiasm for some cheap attempt at marketing.
DPA calls this microphone their 4099 CORE Mic, Loud SPL and describes it for use to close-mike most types of instruments - from banjos to cellos and most everything in between.
One gooseneck mic can be fitted to a variety of mounting clips to serve various applications. A mounting clip has been specifically designed for the acoustic guitar, and is shown in the photo, below.
DPA 4099 CORE Instrument Microphone with Guitar Clip
I consider the DPA 4099 a serious microphone for the most demanding of audiophiles. It may be a bit fiddly to position it, just right, on your guitar. But, unlike a microphone on a stand, once it is positioned, it moves with you and your guitar. It can be used for both sound reinforcement and recording.
Physically, it may take a bit of getting used to, as it is a more delicate accessory affixed gently to the exterior of your instrument. Accommodating a particular pickup system is not unique to this microphone. For example, a soundhole-mounted pickup requires you stop clicking it with your fingernails or striking it with a plectrum. Once you adjust your technique, it is a very sweet sound solution.
You can read more about the DPA 4099 microphone on their website » DPA Microphones.