Think some of the holsters made by the better quality custom kydex guys are cool? How about a holster for a LAAW from S&S Precision? You will still need the sling, but at least it's not slapping your back flopping around while you're patrolling and climbing.
(Note: not really a holster. It's a retention device. Don't be so literal.)
Since not everyone has the opportunity to carry a LAAW around on a daily basis, perhaps this would suit you better. S&S "One Size Fits All"