I would also rebuild it if possible. In fact, other than larger BMX hub axles, I've never heard of slightly larger axles for bike hubs... 9mm is the standard for QR.
Are you sure you're looking at the right axle type? 9mm seems to be the standard for QR wheels and 3/8ths is the standard for bolt on. (I think...)
Wow, if you google around for this, you come up with an interesting thread with the Sheldon Brown (RIP) in it!
https://groups.google.com/forum/#!to...ch/xBc64H0aotk