We have tested several different 'wired' microphones. Most of them are lavalier microphones, which basically entails that they can be used for hands-free operation, and often will have a small clip to attach to your clothing.
Looking at price, performance, and overall quality of the product, we recommend the following microphone:
Movo PM10 Deluxe Lavalier: AMAZON LINK
To use this microphone with Ava, all you have to do is to plug it into your phone, and it will automatically be picked up.