Isolation feet for monitors

I need to isolate my Linn Katan monitors from the bookshelves that they currently sitting on.
System can be viewed here : http://forum.audiogon.com/cgi-bin/fr.pl?vopin&1095824323&view
I have placed a 12”x12” slab of granite between the speakers and the shelves for mass, but now need some sort of isolation footing to separate the speaker from the granite.
A cheap solution would be to insert some neoprene pads beneath the monitors. Has anyone tried this?
Another option would be isolation feet or spikes. Are there any cost effective suggestions for feet?
Thanks