http://www.thg.org.uk/info/plastics.htm
"Small cracks and chips in the bakelite can be filled with soft furniture restoration wax, boot polish (my favourite) or car body fillers (cellulose paste or fibreglass resin types - you can buy these which are already tinted black, intended for filling cracks in black plastic car bumpers). Clean breaks can be joined with Superglue (cyanoacrylate) or Araldite (epoxy resin), though care is needed to prevent smears of glue showing. These techniques work. I know they do and they work very well. "
Good luck, Sandy.
Tom