I don't have much experience with mic-in an acoustic but this might work for you. It's cheap simple and you can adjust the mic easily. First you can read the link below. It says to use shielded wire but it's not totally needed.

Piezo electric mic

Now all those directions are good but you're not done. You will need to crazy glue the metal portion of the piezo to a 1/8th inch thick piece of wood. Maple and Oak work well but anything will probably work. The other dimensions need to only match the size of the peizo pickup. Once this is done you can mount it to the guitar in any place you like. Trying different locations to find the best spot. I would use 2 sided tape or some thing that won't be permanent so you can experiment. I suggest starting by placing it on the back of the guitar and then under the bridge inside the body. Cigar box experience. It only costs a few dollars and can be used on other instruments too.

Just a thought.