Maybe the bearings are "landrover only" but they must be attainable from bearing manufacturer. Bearing production requires massive tooling/investment. Landrover do not manufacture there own bearings. They buy them in. I still believe that if you got a number from the bearing, you could find the original manufacturer.
The only problem i could see would be that an individual may not be able to purchase, as the original manufacturer may require a batch to be made. This makes it impossible for an individual who wants 1 or 2 bearings.
However if Nige is wanting to add it to his business, it may be viable for him to purchase a batch..