I have a Kodiak Backpacker 44 that has the same grip shape. I needed some cushioning for my thumb as the left side wood panel (on all Redhawks) bites a nerve in my thumb.
I have used both a Pachmayer Presentation grip and a Decelerator Gripper grip both of which fit just fine and were much easier on my thumb.
I found the Decelerator Gripper to give big car comfort when shooting even the hottest nasty loads. If you push on the bottom corner you can feel the void if your looking for it, but you would never know it's there in normal use.
The only pic I have of the grip on my Kodiak