Roc has a 0.3db circular dbs dual lnb (CST-12G). Does anyone have this lnb and how does it compare to dish network lnb's and the DPL2: Sadoun DBS Legacy Dual LNBF ?

I just got my new (white) fortec 120cm dish, but there was no 40mm lnb holder. You just shove your square lnb into the end of the lnb arm. I want to put an invacom quad on the dish, but I require a 40mm lnb adaptor or a new arm with the 40mm holder. Does anyone know if such an adaptor exists for...