I contacted benelliusa, they told me to go through midwayusa who couldn't get it, and brownells, which sent me the one piece screw with retainer ring.
looking at my manual, you're right, its called an axle bushing.
according to a parts list it says a retaining ring, spacer and spring plus axle bush go in that hole. i have the feeling i'm missing the spacer and spring meaning my bushing sticks out too far on the breech side.
i have the axle bushing sitting too deep in the hole with the retainer ring holding it in on the outside of the hole. I'm pretty sure i need the spacer and spring. then i can reassemble the axle correctly.
i realize now, that the two piece screw was the retarded side saddle one. and i'm just missing the spacer and spring.
any info on what to ask brownells for would be greatly appreciated. i've never had good luck finding stuff on their site.
Thanks!!