I like the waist packs and bags from PacSafe. The waist packs have a cable in the belt that is cut proof so you don't have to worry about a slash, grab, and run. It's also lockable.
I have one of these in the older model that is orange. I like the brown better but Sierra Trading Post had it cheap. I use it for my P-3AT, wallet, etc. when traveling and car camping.
It comes in two sizes 100 and 200 (click the number in the product name on their site to see either one). I think I have the 100. For your Ruger the 200 might work better.