It is possible to get rebuild parts for shocks. I don't recall where, but know they're available. I agree with bmweuro - rebuild them yourself - getting them open is the most difficult part of the job.
AW - I think you're confusing the two different shocks known as WP. I believe the BMWs came with White Power shocks, not Works Performance.
Wanted: Dead, smashed, crashed or trashed gauges
BMW GAUGE REPAIRS - TACH*SPEEDO*CLOCK*VOLT METER *PODs & LIGHT BOARD*