I have performed with success a diopter surgery. And it is very cheap, the slight problem is in the installation. The diopter is this http://www.ebay.com/itm/NIKON-EYEPIE...item5af1e0f6f5
And there are lots of them in the market.
After you have purchased yours, you have to extract the diopter glass from the plastic frame.
Then you have to remove the front plate of the camera. If you find a resistance, probably you, like me, have forgotten that bloody screw under the leatherette.
You will inserting the diopter on the right front window in the following way:
1) You will find a black frame which is not attached to the camera and behind it a removable rectangular glass which is there to prevent dust entering the camera. This glass will be removed forever and the diopter will fulfill this function, but not in the same space. The nikon diopter will be sticked on the back side of the black free frame. The side it is not painted.
2) In your way to sticking, you will notice you are very scarce of space to stick. Therefore I used a simple tweezers to hold both pieces in place. But in order to free both of your hands, as well as keeping the parts aligned, you should wrap the tweezers with any kind of elastic band and then put both parts in place.
3) Then you need a liquid rubber gum, of the lowest quality kind, that shoe fixers use and are sold at any technical store for pennies. It is not the kind of instant fix, but the one of yellowish color.
4) You SHOULD NOT glue the parts while the rubber gum is in its liquid status, otherwise you will mess the whole thing. You should use it after you have poured it on any surface and it becomes half hardened, because you will be pouring the gum AROUND the diopter glass.
5) Then you re-install the black frame in its former space. The rectangular former glass will be trashed, i.e. you will not use it
Its space will be used by the diopter which will act to block dust.
Now four further notes. a) After you have glued the diopter to the back side of the free frame, you will notice there is micro metric free space in the corners allowing dust to enter, because the nikon diopter is not rectangular, but the horizontal borders are rather curved. You will fill these very small spaces with the hardened gum, if the space was not filled already, by the rubber gum residues.
b) Since the screws are quite small, you are strongly recommended NOT TO PERFORM THE SURGERY ON ANY KIND OF TABLE. I recommend you to do it on your bed sheet, when they are on your bed, deep into the space.
c) In you way you will discover a terrific way of lifting micro screws: using half hardened glue on the screwdriver and then inserting the screws with ease.
d) I am not sure by definition since my vision requires diopter correction, but it seems to me that the sides of the nikon diopter, front and back, are not equal in their function to correct your sight seeing, but one surface is better than the other, therefore act accordingly.
For year and years, decades and decades, centuries, I have been walking in the wilderness to find a solution to this diopter stuff. Let's time to say if I have already found it.
Kindly excuse me for all the errors in English, adding to my errors in the language, I was in a rush to write another post.
I did something similar with a Contax diopter. The Contax diopter is a free lens with no plastic frame. I affixed it to my Rollei SL35M. I used silicone glue.