I noticed when filming outside with my Atomos Ninja 2 that, because the screen was so reflective, it was hard to see what was happening on the monitor. I looked on the internet for solutions, but I couldn't find anything of use, so I decided to model and print my own. To print one for yourself, download the STLs and import them into your print controller. I modelled this using SolidWorks 2013, so to check out the source and make modifications you'll need to download all the SLDPRT and SLDASM files.I printed this on an HP uPrint SE Plus in white ABS, so that I could later spray paint it black. Cut the eyecup off a cheap eBay viewfinder (like this) using a mitre saw, then hot-glue it onto the viewfinder body. Get a GoPro mounting bolt, also from eBay, and it'll fit together nicely.