Brembo themselves generally don't sell rebuild kits for oem stuff to the public due to liability issues from DIY repairs.
AP racing who are part of Brembo can probably service them for you.
Ducati however will supply Brembo parts that others won't but many dealers will not advertise the fact. I have never found any kits in the Uk but this bod in the US sells a lot of Brembo spares and might be able to help. http://shop.bevelheaven.com/SearchResult.aspx?CategoryID=35
Several guys on the Ducati forums use him for Brembo parts.
Oh arse. Ima ttry to find out o-ring sizes and source some locally. Aprilia don't make o-rings, so any motor factor / truck repair shop etc should be able to supply for pennies....