Instead of spending $$ on a monitor that is going to add more wear and tear on you, I would try shooting tethered or using an eye-fi card if your camera supports it.
You have to look at it this way, the more gadgets you add to your camera, the heavier it becomes, thus making even short photo shoots unbearable due to the added weight strain of your camera, lens, flash and anything attached to your camera.
Shooting tethered has some pro’s and con’s but might be a good alternative. Depending on your camera type and model, it may be as easy as setting up your camera to shoot with an app to a tablet or laptop/notebook. At least with that option, you can see the images as they are shot on a larger screen. Also a good selling point for clients to see the shots as they are taken.
The con – a tether that may cause a tripping hazard or get caught up on light stands and such.
Another option would be to use an eye-fi card to shoot wirelessly to the same tablet/laptop/notebook. You will have to see if your camera model and card type are supported.