My opinion, FWIW, is that off-body carry should be a last resort, but I also know everybody's situation is different and we gotta do what we gotta do.

I would second the suggestion for a good belt and suspenders. I have a set of Perry Suspenders and they work quite well at redistributing the weight off the waist/hips because they attach directly to the belt. While I don't use it that much, when I did I wore it over my undershirt and under my over shirt.

A shoulder holster may be a viable option. Your clothing may affect how useful that might be.

If you do need to do off-body carry, you have to watch it like a hawk. Laying it down somewhere and forgetting it can be real bad. Not to mention the possibiilty of theft.

The closest thing to off-body carry I've done is in a fanny pack, and that's only when I went jogging. The one I have is small and doesn't scream "GUN!" It holds my 642. Anything bigger might be more of a tell. I once saw a protection detail where all the team members had fanny packs. They made it pretty obvious.

I like the day planner option. I know there are companies that make purpose-built day planners designed to conceal a gun.

A backpack might be an option. I may be wrong, but I recall seeing a concealed carry backpack that had a quick-access hidden compartment for your gun so you could get to it without having to remove the backpack first. Another benefit is that you could probably stick a panel of soft body armor in the bag for some extra protection.

There are also messenger bags, basically a briefcase with a shoulder strap. Some are more formal than others. I'm sure there are models designed for concealed carry of a firearm.

Hope that helps.