part for door lock

I purchased an F-10 French door from windows doors and more in 2000. One side has a door knob and deadbolt. The other side which is fixed (can be open but not with door knob) has the receiver for the door finger and the dead bolt finger. The finger slides through a brass plate with a hole in it which is affixed to the fixed door by a plastic plate like thing. This plastic part has fractured in the cold on the door knob piece and I need a replacement.
Do you have the replacement part?
Must door be removed to replace for can the plastic part be snaped in?

Thank You.
Carl