We used to be one of the Importers for JConcepts products & stocked parts for the BJ4.
Now JConcepts used SMD to distribute there products to the shops in the UK, unfortunalty they do not list the parts for the BJ4, so that is why you can not find anyone in the UK that stocks the parts.
If you need parts you will have to order them directly from the JConcepts web site.
Hope that this helps
Marc