I went down to a local Fastenal and they didn't have any in stock but could have ordered one. So I went to Sears to check out their inventory, just so happened to have a T-15 torx with a 6" (~15cm) long shaft (make it 10 5/8 if you include the handle) that just barely fits.

If the computer has never been opened or not opened much, you might need a "Case Cracker" as it was called in the day. The alternative that works just as well is a solid putty knife. The idea is to run it along the edge to free it, not pry it open like you're underwater and found a large case of expensive riches.