Yesterday I finally managed to get my hands on a The Valve 112-RFX closed back cab. They're hard to find at the moment and when yoy see one it has a different tolex or grill-colour. But, I found a matchting cab, with discount at Max Guitars in The Hague. Still 340 euro.
They also had a TC Electronic Spark Boost on offer (99 euro). so I grabbed that one too. It's a poor man's AC Booster. :)