Oh,well in that case I'd suggest a SOB holster,or some pants with looser pockets.
SOB is now my favorite way to carry. Its easy to get to while sitting,and the holster positioned just off center (between 4 and 5 o'clock).
Its also completely hidden by the back of your chair while sitting.
I know you said bad back....Ive got a bad back too,and I am comfortable carrying that way.
Ive also got some hyper-sensitive areas on my back from nerve damage.
Now when I say hyper-sensitive I mean a finger nail scratch feels like a knife being plunged into my skin,so If it works well for me,it might work for you too.
Ive also found that a SOB holster works surprisingly well on your hip at a 3 o'clock position.
It will give you the perfect amount of cant for an uber easy draw while sitting while keeping the muzzle up and out of the way enough to keep it from digging into your seat.