I you have the carpet spikes they fit the same aluminum inserts as the rubber feet ... i'd check and see if the inserts are screwed into them

In picture from left to right: Spike, rubber foot (newer?), rubber foot (older?), aluminum insert, and
in front of that the screw which holds insert to speaker

[Linked Image from i.postimg.cc]

If the you call them with the order I'm sure they will supply the insert and screw if you request them.