MacBook Air [A1237] New Hard Drive, but no OS disks.

Hello. I have a Macbook Air whose hard drive finally gave out. I was looking into buying a new one, as the computer itself works fine (and suits my travels) but don't have the restore/OS disks. I had planned to do remote install but now am at a loss. So how can I get the original OS on there? Can I still order disks from somewhere? Any help would be greatly appreciated.

{MacBook Air 13" Model #A1237 1.6 GHz one.}