Use seatpost "U" shaped part.

[goneriding]

I'm after the "U" shaped bit that goes under the seat rails.......


The 3rd bit down in the pic, though I'm sure you all know...

 

[mk one]

Was going to post link but judging by pic you have found it already

Not sure if you can still buy the rebuild kits new :?

 

[Rfriend1975]

If you are still looking try the user 'synlos'. He makes one for a Syncros post which looks very similar.