You could use plastic P-Clips as an alternative.
http://base.google.co.uk/base_media?...8430928&size=1
Cut off the 90 degree bend (on the right in the picture) and make a new hole. You've now got a flexible U-shaped bracket.
Now fasten one side to the drive using the standard fixing screws, and fasten the other side to the floor of the case using a small screw and nut.
The natural springiness of the plastic should dampen any vibration, and at the same time it will be fairly secure.