I ordered most of my stuff from Mouser. The transceiver chip ends in 234 which is maybe why you can't find it. Here it is at Mouser: http://www.mouser.com/_/?Keyword=SN65HVD234&FS=True
You will need one of those chips for each canbus port (so, two per Due) and some misc other goodies (60 or 120 ohm resistors, small value capacitors, etc). Also, use a schmartboard 1.27mm arduino board which is part # 206-0004-02 (also available at mouser). This board has a place to put the transceiver chips as well as having pins that go into a normal arduino board. It is not the proper size for a Due but you can run jumper wires to the proper pins of the Due. It's sort of a cobble job at the moment but it does work.