I ordered the EVF thanks to this great thread. Shipping took around 3 weeks to Germany and I had to pay 20€ extra. 215€ total. Thats not even half the price of the Sigma FP EVF.
Unfortunately it does not work 100% with the Sigma FP. The camera screen flickers when I plug the EVF in and once in a while a frame appears on the EVF. After switching the settings of the HDMI Output in the menu a couple of times it eventually always works. Sometimes it takes 1 minute, sometimes 10 seconds, but after I switch off the camera it's always the same issue again.
At first I thought it wouldn't work at all and that the HDMI power of the FP was not strong enough but once the EVF works it does so without a problem until I power off the camera. For focus the image is nice and mirroring the camera display works great, with peaking, false colour, magnification, etc. The blacks are crushed (and have a green tint), so for exposure it is not as useful.
If it wouldn't be for that annoying connectivity issue this thing would be perfect. Paired with the 28-200 this finally makes my stripped down "Bolex FP" complete. Being able to adjust the EVF freely and keep the camera close to my chest is really comfortable and the Lens Stabilisation makes the FP viable for handheld while still being compact and light.
Think I'll be using this for slow paced personal projects or when I am filming constantly and dont turn off the camera a lot. The form factor and not having to think about extra batteries is great. For photography in sunlight I'll still have to use my diy loupe for the backscreen because waiting up to a minute for the EVF to finally work is just to cumbersome.
@Clark Nikolai Do you know if the buttons on the back have any functionality apart from the one that changes brightness?