Don't know about the R200 pinion bearing, but I'm told the R180 one is NLA
Depends how hard you look!
http://www.ebay.com/itm/NISSAN-DATS...Parts_Accessories&hash=item27db773048&vxp=mtr
http://www.ebay.com/itm/Datsun-240z...Parts_Accessories&hash=item563e92c3a7&vxp=mtr
Nissan didnt make bearings themselves . Youcan even see the NSK numbers one one pic.
Here is a R200 version.....................
http://www.ebay.com/itm/Datsun-240z...Parts_Accessories&hash=item4acfb02ee7&vxp=mtr