Hi Ryan,
Unfortunately we cannot direct you to the file, as distribution of the software is against their copyright/EULA etc.
VATSIM also does not allow this type of request.
Best suggestion I can offer is to check a used game store to see if they have a copy for low cost, contact Microsoft (at one point they would be able to ship just the #4 disc at cost), or look at several disc tools on the market in an attempt to seal the holes.
Regards,