"We have just released screen protector SP8321 for Nikon D800. ..."
I think the SP8321 would also fit the D4 and the D600 just right since I visited Penn Camera in Rockville, MD on Friday, 16 November, and measured the 3.2" diagonal screens on all three (not touching the D600 or D800 in the process): D4: 67 mm x 51 mm D800: 66.5 mm x 51 mm D600: 66.5 mm x 51 mm The width of the D800 and the D600 LCDs are probably the same as the D4. My measurements were probably off a bit due to parallax.
It seems that our problem is that the Giottos USA Distributor has some bushel baskets of SP8306 made for the Rebel XSi, and will not import the SP8321 until he sells off his SP8306 stock.
On Tuesday, 13 November, I visited Best Buy in Laurel to measure the 3.0 in. diagonal screen of the Canon Rebel XSi. They didn't have any. They said that it is an old model. I checked and it is still an active product per the Canon Web Site, but is about 4 1/2 years old. I noticed that all the current Canon models at Best Buy have articulated LCD Screen systems. The screen can be swung out and tilted. When swung back in to the recess in the body, it can have either its plastic back exposed for storage, or the LCD panel exposed for use. I think that there is not sufficient clearance for an accessory glass screen protector to be used with the screen pointed in to the storage cavity. It might be hard to sell off that stock of SP8306's.
By the way, I was surprised to learn that the D600 and the D800 are equipped with plastic screen protectors by Nikon. I think that they are intended to protect the screen when the camera is in a bag, and are generally to be removed for use, at least in benign environments, like tripod use in studios.