I'm referring to the bearings that are placed at the bottom of the blade holder, the side that sits on the metal tail shaft.
By inspecting it I came to believe that this is the cause of the hunting I get while piroing, because it makes the pitch slider sticky. When I rotate a single blade holder by hand, I can feel it moving a few milimiters at a time, as if it's toothed inside or something.

I couldn't find a part number anywhere, so any help would be greatly appreciated.

Sounds like the bearing are gone. Getting everything moving nice and smootly will go a long way to fixing your tail wag.

Those bearings are are MR52ZZ's.

Thanks khaoz.
I just found this picture in Align's site which describes the parts forming the tail.
It appears I need the MR63ZZ part. The MR52ZZ sits inside the blade holder, and it seems to work alright. But I just get these as well, just in case.

Thanks a lot for your help.

Well it seems I got the wrong part...
This tail in the picture above is the new tail with the raised axis, that the blade holder is placed onto. Mine is the older part without the axis, and the bearing that in the picture is supposed to be MR63ZZ, should be something else in my tail. The inner diameter should be smaller than the MR63ZZ. I don't have a caliper, so I can't tell exactly what should it be.
I'll just keep on looking for the right part. Too bad.

Took me exactly 3 minutes to find out that I needed the MR62ZZ and not MR63ZZ... Yep. When your brain doesn't work, your legs work harder...