Those are just an ordinary 6004 and 6005 ball-races Mark, you can get them on any street corner:
http://www.ebay.com.au/itm/Deep-gro...d_Tools&var=&hash=item258e82275eI had to put new main bearings in an Echo trimmer recently and used sealed ones instead of open ones because they were cheaper. However to do that you have to check two features. First, measure the actual width of the old and new bearings, making sure they are the same. My sealed ones had a slightly wider inner ring, so I ground it down to the original width. The other issue is whether or not you have to remove the rubber seals with a knife point or scriber. Some engines rely on having fuel/oil mixture pass through the bearings to lubricate some other feature of the engine, but most do not. After having a close look, I left the seals in place, and the Echo engine seems to be happy that way.
