Or you could cut side vents into the coat or jacket like I did with a heavy winter pea coat I purchased last year. After measuring and cutting the side vents I then went out to JoAnn Fabric and matched the fabric for my pea coat and had a tailor sew the coat back up in such a professional manner that it looked as if the coat was purposely made with the side vents.
Where I live we have a huge stray dog problem, they roam in packs and tend to come out when it's dark to forage for food. When I'm brushing/scraping off snow and ice from my vehicle in the darkness of a winter morning/evening, and I spot a pack of strays near me it gives me great peace of mind knowing I can still acess my weapon in a flash, cutting the coat was well worth the effort.