My dvd recorder seems to have a part mis...

my dvd recorder seems to have a part missing from the drive itself
the bit is missing that holds the moving laser optics directly to the spiral grooved rotating bar
i have a shaped white plastic screwed to the metal of this lens assy and then a gap where something must go to hold this assy onto the tranporting spiral brass coloured metal mover thingy.
if i could get what ever it is or have to replace the internal dvd recorder drive make unknown

any ideas