Have someone locally that can download it from their purchase history? You could then make a bootable USB drive with Mavericks on it. I keep a USB of each OS X.
I have an old (late-2011) MBP that shipped with Lion. I've kept it on Mavericks b/c I've heard that the newer OSX's are very CPU-intensive and, like I said, it's old.
Anyway, my OS was corrupted by a faulty-logic-board-induced kernel panic, and now I need to reinstall Mavericks, but it's not in my purchase history.
Can you perhaps upload&link me to this copy of yours? I can make a bootable drive from there; I just need the raw OS.