Indeed.. well if any place will carry them, it'll be them.
No idea what this places' reputation is, but they seem to indicate it's possible and available:
http://www.dttservice.com/macbookpro.html#macbooksuperdrive
I suggest Googling for more, that's how I found the above.
EDIT: I should also say that because drivers are an issue (there generally aren't any readily available for OS X), you cannot (usually) simply purchase a replacement drive off say newegg and slap it in your Mac. You also might want to look at
http://www.patchburn.de for indications of what 3rd party OEM drives might be swappable.