I have exactly the same problem.
I know the rack came from Moss as I have the invoice from the previous owner. They are made in Argentina and are LHD Mini upside down.
The catalogue and the website show no parts at all.
I have spoken to Moss and that is the situation, they don't sell any parts. But, also not shown is the fact you can buy the rack separately.
As I don't want the car off the road for long I have settled for that option and it should be a one off, one on situation.
With VAT and postage it is about 200£. I am waiting for someone to bring it out from the UK