Cheapest way to obtain the bearings, seals, bushes etc. is to buy a complete refurb kit from Wemoto.

http://www.wemoto.com/bikes/yamaha/xt_660_z_tenere/08-09/picture/swinging_arm_pivot_bearing_kit_slinky_glide/

Even from a bearing supplier, the individual bearings for the swingarm/linkage don't seem to work out a lot cheaper than OE in my experience (unlike those for the wheels and headraces).

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