The Mac OS X 10.9 Mavericks download script is now hosted on Mavericks Forever. To download Mavericks, open a Terminal on any Mac and run:
curl mavericksforever.com/get.sh | sh
Or, navigate directly to mavericksforever.com/get.sh to read what the script does.
A bit late to the party, I just stumbled upon this thread.
I have a working installer for 10.9.0, and from there you can update to 10.9.5. I used to be a tech and I keep an installer of every MacOS version since 10.6 on a hard drive in case I need to reinstall stuff offline, and also because I don't trust online repositories to be available forever. Looks like I was right about that for Mavericks. I also have working images of 10.9 and 10.11 modified for 32bit to run on the 1st gen Mac Pro.
Happy to share if anybody needs it.