PKR
Veteran
If your camera has a removable focusing screen or protective glass over the EVF, this may be a solution.
http://www.katzeyeoptics.com/Gridlines.html
Edit: from reading, it looks like they're out of business. There may be other people doing this work.
http://www.katzeyeoptics.com/Gridlines.html
Edit: from reading, it looks like they're out of business. There may be other people doing this work.