Well before you go and spend loads on a new steering rack, try this first.
Does it happen all of the time? Mine only seems to happen when the car is hot, or the weather is.
If you take it to a garage they will probably charge you a hours labour for the greasing of the mounts. As it involves removing the whole suspension set up and re-greasing the top mount. You may be able to squirt some WD40 in at the top of the mount in the engine bay, but that will be nothing to actualy getting into the mount.