I use a Maxpedition style bag that can be slung cross chest, but mine's made by Tactical Tailor. Allows me to carry a spare mag, flashlight, knife, and whatever else I need should I have to get out of bed in the middle of the night and arm myself. I sleep in boxers and a T-shirt, so I prefer to not have things hanging off my waist if I can avoid it.
Otherwise, the easiest and quickest set up, to me, would be a nylon style police gunbelt (cheap ones can be had by Uncle Mike's and you can go up in quality from there) with a decent holster made for the gun.
Good on you for considering this now so that you're ready for the next weird knock at the door as you clear cobwebs and try to focus. Not the easiest thing at times!