I've been looking into this too. So far I've found that there are a couple of 4 point harnesses that are ADR approved. One is made by Autotecnica and is reasonably priced. Check out the harnesses on their web page
Autotecnica
The only problem with the ADR legal harnesses is that they are only 2" webbing and they all uses a traditional deatbelt catch. None of the 3" wide camlock belts seem to be legal at this point. It may be because it's possible to only half do up the belt with a cam lock setup.
Cheers