Making or obtaining replacement parts for a multi-point window locking mechanism
Espagnolettes

For reference, what I eventually discovered was that these parts are called espagnolettes (in the UK at least) and that you can buy generic replacements that can be cut to fit. 

There are a limited range of common rail-widths and lock-backsets that you need to measure before ordering. Fashions change, so older style parts are harder to find.




  Dimension A - Backset
  Dimension B - Mushroom Height
  Dimension C - Rail Length
  Dimension D - Rail Width  


A suitable search term might be "upvc window espagnolette"