Secondary glazing part

[stayclean]

Hi
im looking for a part which fits on top of vertical sash for secondary glazing. ive attach a photo showing part im looking for manufacture name or a supplying of these View media item 83971 View media item 83971

 

[stayclean]

hi
the part im looking for sits on top vertical slider, its job is to keep aluminiun sash in frame and guide sash in slider of frame as you can see by photo part go around tension spring. has any body any advice , trying repair seconary glazing.
thanks