Poserworld has a cowboy outfit for Mike with an open vest and numerous textures.  Although, I think it's for Mike2.  But since it's an open vest, I'd think you could easily fit it to Mike3.  There's an open pirate vest there that's for Mike3.  If you're not already a Poserworld subscriber, I highly recommend it for anyone frequently in need of clothing items.  They have a good collection of props and scenes as well.   

Irene-