Conveyor belt motor

[t41w4ne5ef0b]

Ok...so I'm trying to make a conveyor belt system for my team's robot, and I've decided to do the PVC/surgical tubing design. For the motor I was planning to use the motor that has that plastic gearbox attached (i dont know what its called, i'm one of those ppl that pays attention to what it does more than names). It's the one with the slotted plastic as the output from the motor. I was wondering waht size bearing fits inside the black portion (cuz from what I can tell, thats what goes in there) plus what size of PVC will fit over the white wheel cuz im thinking of just shoving it on.

BTW if anybody else has diff ideas as to how to do it PLEASE tell me...our team is VERY short on devoted members (i only see 2 other ppl after school on a regular basis ) and we dont exactly have accessible funds cuz our school club system is retarded and we have to go through a lady to get money out, but tahts for another post