Peugeot 206 2004 3dr penger seat doesnt lock, it moves backward and forward?

a few days ago, i was hoovering my car and when i tried to get in the back seat, i heard a click, later i found a very small lock hatch broken in between the rails. i took it to garage, they want to change the whole rail and it costs �250 including labour. is there any cheaper way to find the hatch or lock whatever it is called.