Hi everyone--
I realize this is a reply to an 11-year old post, but I figure possibly it may help others even at this late date.
I recently purchased a D80 on eBay that came without a hard drive key--
After looking carefully at pictures of the key and doing some research, I learned that this is a standard barrel key that's readily available
everywhere. I found a set on eBay-- It's called a "235 Barrel Key", (it's marked with a code "235" on the grip) and can be used for anything from motorcycle compartments, to toolboxes, to luggage, to Fostex D80's! Sure enough, when it arrived I tried it and it worked perfectly. Under $10 for a set of 2 on eBay. To unlock the drive, you insert the key with the notch at 9:00, push in with some force, and turn it counterclockwise to 6:00. Then the drive will just pull straight out.
Hope this helps!