not only has the RD become a seller's market item, but people who have the expertise to restore a RD charge a bomb to do the same.... not to mention the spares of course.
The best way would be to buy a not so well maintained or ill-conditioned RD and then splurge on restoring and modding it.
In any case, be prepared to shell out an amount in the 80k region, and if you have the money brother, there's nothing like an RD.