After a few inquiries and emails I have been able to order a one off set of leads for an 18rg model number: B4664i (from the catalog)
They make one offs in between runs at the factory. So if you want a set of Bosch leads for your 18rg I suggest ordering *very* soon to minimise the wait. From memory the price is $66 (+gst?), but don't take my word for it and you will probably have to leave a deposit. Waiting time should be less than one month.
If when you go to order them you are told that they do not do one-offs, you are talking to the wrong person I suggest using the contact links on the Bosch site as they got back to me very quickly and helped sort out the problem.
If you are in Newcastle I highly recommend Alan Whitford at Glendale Auto Electrics as he has gone out of the way to help me, he knows who to talk to to get things moving and has probably spent all of his margin on STD calls to sort out the problems. Alan is on Lake Road, Glendale, just up from 'The Warehouse' and can be reached on: (02) 49549170.
His details are also on the list at the Bosch Site.
I haven't used Bosch leads before so someone may wish to comment on their experience. But from the technical details I have read and their warranty they sound pretty good.