With the info provided, I would recommend a wireless lavalier mic. Trying to boom an on-the-fly “walk and talk” can be very difficult. Think about boom shadows, doorways, narrow corridors. If you have them, and want to get fancy, use 2 lavs, one on either side of his chest (on the jacket lapels for instance), to help with head turning while speaking. Or, best of all, hire a sound guy!