The AccuShot monopod is a very mobile and lightweight solution for supporting the rear of the rifle. Though it may not be quite as stable as a rear bag, it is a hell of a lot easier to carry and is always attached to the rifle.
I'm using the BT13-QK rail version, attached to a McMillan A5 via a Seekins SRS rail. If your stock can accept a rail, that would be IMO the best way to go.