Upgrade vom 10.8 to 10.9 all of my Macs are running OSX Mavericks right now, except one iMac that is still on OSX 10.8.5
I've tried to find a possibility to upgrade to Mavericks, but can only find Yosemite upgrades in the appStore - is there another possibility up upgrade that machine?

Thanks for your hints and ansers,

Thomas
Update: I just found out from this answer Where can I get a copy of Mavericks after Yosimite has been released? that it is possible to download if you are a member of the Apple Developer Mac program. 

I tried the link from the US Store https://itunes.apple.com/us/app/id675248567?mt=12 but it appears it is not available anymore.

I found this from reddit http://www.reddit.com/r/osx/comments/1oey0b/download_os_x_109_mavericks_gm_final_dmg/

This is the link http://www.techglobex.net/2013/10/download-os-x-109-mavericks-gm-final.html


  Download OS X 10.9 Mavericks GM Final .DMG Setup File (Build: 13A603,
  Latest, V2) - Direct Link | Link 2 | Link 3 | Link 4 | Torrent Link |Link 2
  
  Download OS X 10.9 Mavericks Server GM Final .DMG Setup File
  
  Download Xcode 5.0.1 GM (Build: 5A2034a) Download iPhoto 9.4.7 Seed
  
  Download Remote Desktop (Build: 370A61) Download .DMG Extractor for
  .IPSW Files - Direct Link


Make sure you check if it is legitimate https://support.apple.com/en-us/HT202369


  For OS X Lion or later, locate the lock icon () in the upper-right
  corner of the Installer window’s title bar.
  
  For Mac OS X Snow Leopard, a certificate icon is shown instead.