how may washers do your screws have?
The only way i can think of to make such screws would be with a metal washer and two foam discs and to make the screw holes in the HDD housing bigger so the screw does not touch them.
explained slightly better:
The screw head or thread must not touch the HDD housing
Some sort of foam washer each side of the HDD housing
an extra metal washer on the outside of the housing
so
<screw head><metal washer><foam washer><screw goes through HDD housing><foam washer><Hard Drive>
The foam discs would be compressed between the metal washer and the HDD (and this pressure also keeps the drive in place

) but if it is too tight then the foam will transfer the vibrations (instead of allowing the drive to move slightly)