After some experimentation, I found that the Doug Ritter PSK rides quite well in my cargo pocket on my left thigh. If this will work or not will depend on your personal preferences and the exact configuration of that particular pocket on your particular body.

If this doesn't work out for you I would try splitting the contents among the various pockets, keeping everything as flat as possible.

The most comfortable spot is no doubt the upper front pocket of my goretex anorak, but that isn't always on me, and it needs to be removed every time I change the number of layers. And it's nice to free that pocket for other stuff. But if you know for (almost) certain that this particular jacket will be used whenever you are actively doing some activity (and only removed to adjust during periods of inactivity) then this may be a good trade-off.

For me, a west will be nothing but cumbersome. I have enough garments to meddle with as it is.

You could also consider a pouch around your neck, possibly with a sling under one arm (such as concealed gun holster). Wear it on top of whatever garment you won't remove during the day, and positioned exactly where your backpack straps aren't.