Will replacing the data-cable replace the broken-off piece?
If not, then for about $30, you can buy a new "empty" external case, and then "transplant" your current disk-space into the new case. Take your current external drive to the computer-store, so that the new case that you buy will be the correct case for your existing disk-drive.
Of course, because you have a "small" (100GB) disk-drive, any warranty for the disk-drive probably has expired, and it would be good "preventative-maintenance" to buy a new external disk-drive, before your current disk-drive unexpectedly "quits" on you.
Answers & Comments
Will replacing the data-cable replace the broken-off piece?
If not, then for about $30, you can buy a new "empty" external case, and then "transplant" your current disk-space into the new case.
Take your current external drive to the computer-store, so that the new case that you buy will be the correct case for your existing disk-drive.
Of course, because you have a "small" (100GB) disk-drive, any warranty for the disk-drive probably has expired, and it would be good "preventative-maintenance" to buy a new external disk-drive, before your current disk-drive unexpectedly "quits" on you.