Pete, recently I managed to break two of those trying to refit them. I found spares on ebay. However rather than keep breaking them I cleaned the fork seat and pushrod ball end and stuck it in place with a dab of silkaflex and supported the rod overnight on a rag while it cured. Slave fitted fine the next day.
Lots of various forum posts by those who say the clip is only there for slave refitting and bleeding. It isn't necessary afterwards. If it were it would be much more substantial.