Hi, I keep a 12ga pump gun nearby at home and would like a shoulder bag that would hold at least a box of 25 rounds, have a comfortable shoulder strap, maybe an auxiliary pouch and a bonus would be a few 12ga loops on the outside for fast access to extra ammo. I'm hoping someone can recommend one like this. The other option would be a small canvas haversack with an "ammo sling" for a strap I would build myself. Any suggestions?