I just re-greased mine. I have never seen or heard of one wearing out? But I may be wrong? Is yours noisey? There isn’t a lot to the racks themselfs so not really a lot of serviceable parts. If it’s still working fine just re-grease it and clean it up.
Im sure most the parts out a LHD rack can be swapped but it would be a waste of money to buy a New LHD rack just you used the new bearing and/or bushes that you may damage by removing