I don't see anything on the sas-tec site that indicates they're CE approved for motorcycle use. Maybe because it's a German site we're supposed to assume they are?
I have a Joe Rocket branded Force Field protector that I like. It's ventilated, a bit, so it's cooler than some of the others. The real issue for the OP may be finding something that fits in the pocket in the back of the jacket. Every manufacturer has their own shape. The Forcefield, for example, won't fit in a First Gear jacket, which is what made me choose the Joe Rocket.
http://www.forcefieldperformance.com/product/upgrade-back-inserts/2361
It seems like you could cut it to fit without affecting it's impact absorbing abilities, but I've never tried to cut it, nor have I tested it's effectiveness. Like Scottie says, the Forcefield stuff gets good press.
NewEnough.com / motorcyclegear.com sells the Joe Rocket version, as well as several other brands:
http://www.motorcyclegear.com/street/armor/back_protector:_installs_in_apparel/