Well, I just did a search for 69.dat in my FFXI directory, and it came back with 165 results. Yes, exactly 165 different files all named 69.dat, albeit in different directories. If you could somehow find out which one it is you need (does it tell you a directory as well as the file name?), then I could upload it to some webspace of mine for you (none of them are very large files).
However, what exactly do you plan to do with it if you manage to get it? Does the installation automatically quit after it gives you this message, or does it give you the option to locate the file manually? If the former, then I really don't see what good it will do to have the file on your hard drive. If the latter, then why not just make a "dummy" file (create or rename a file on your compter as 69.dat) and just point the installation to it? There's a good chance it won't check the file to see if it's the right one, and considering the vast amount of files the game uses, it probably won't cause you too much trouble while playing the game.