Slight thread ressurection, but I can vouch for the SPES back of the head protectors (the 'Vectir' one that comes in two component parts).
I've had one for a few months now, and it fits and works perfectly on my black Leon Paul 1600N coaches mask. I got both bits, the mask cover and the occiputal overlay - they work together as a unit. If you already have a sabre cover on your mask, you can use the occiputal alone, but you may need to rig up a piece of velcro to hold it in place.
SPES also have a couple of one piece deluxe 'hoodie' units for the mask, but they were a bit pricey for me, plus I think you would have to get the sizing perfect on those - I've seen pictures of the deluxe leather one over the top of a mask that was too small for it, and it looked awful.