BERTYBOY01

I have a Xantia Activa 'P' reg. Petrol. We have a hydraulic unit on the o/s/r suspension, it acts on the the antiroll bar as some kind of hieght corrector. Sorry to be vague but i'm not sure what it is called. It is only fitted to the Activa. The genuine part no. is 509004. Mine is leaking and has failed the MOT. Does anyone know where i can get hold of a second hand unit. They are £270.00 + vat new. Any contacts of second hand unit would be gratefully appreciated. Can they be refurbed?