Can you add the resolution as a custom one to your video driver? I had to do something along them lines to run my tv at its native res, and every game I've tried on it has picked it up fine and gave me that option.
Computer monitors tend to have an option to accommodate smaller resolutions correctly, it won't fill your screen but it won't look horrible and stretched. Alternatively there were some external software alternatives available (Kegytes made one) but I don't know if anybody has made one that works in DX9 yet because most games by decent developers now no longer find setting resolution correctly a major issue.
Its somewhere in my Nvidia drivers..it might not be a standard option, might be worth spending a few secs with Google. Not that I would go to such lengths for this game