There's 4 used on the REAR of the glass rails that collapse.
They are $18.37 each here AUD

To replace that end bush:
Wind the window down.
Remove the two window stoppers held on with 10mm bolts.
Wind window up past the door frame, then tilt the window forward exposing the bush.
The bush is held on using a bolt through the middle and washer on the back of the window.
Using a Torx attachment and pliers undo the washer and the bush comes off.
Then just put it back together.
Try to align the stoppers in their original position, otherwise the window wont close properly.
If there isn't a bush, bolt or washer there, check the bottom of the door, they often fall out !
The vertical wire guide rail also has one that can be replaced with a 27mm shower/door
roller guide. Just haven't done that yet myself - How to guide to come shortly..

What's needed - 4 shower door rollers & a pair of 'slip joint' pliers as well as the correct rear roller bushes.
The rollers need to be with the attached post & come with a 10mm nylock nut, the pliers are available at a lot of $2 shops for $2 (lol) & the jaw end of the pliers need to be ground down both sides by about 50% so that you can firmly grab the post of the roller whilst tightening the 10mm nut.
Obviously you need to grind,cut off the existing post & punch it out thereby just leaving a hole in the frame where you then bolt on the shower screen roller

Photo guide in Japaningrish (lol)
Page 1:
http://translate.google.com/translate?sl=auto&tl=en&js=n&prev=_t&hl=bg&ie=UTF-8&u=http%3A%2F%2Fminkara.carview.co.jp%2Fen%2Fuserid%2F273614%2Fcar%2F402822%2F1917616%2Fnote.aspxPage2:
http://translate.google.com/translate?sl=auto&tl=en&js=n&prev=_t&hl=bg&ie=UTF-8&u=http%3A%2F%2Fminkara.carview.co.jp%2Fen%2Fuserid%2F273614%2Fcar%2F402822%2F1917616%2Fnote.aspx_________________________________________________________________
Speed is subjective to only how far you keep your right foot down..
