Take one of your Vandersteen spikes to the local hardware store and purchase either hex or carriage bolts with the same thread size. They won't harm the floor and will provide solid contact and can be adjustable for desired tilt. This will cost less than $5. Another option is to find similar products from an audiophile web site and pay $100+ for similar, but much fancier, product.
The hardware store option worked great on my Meadowlark Shearwater HRs.
The hardware store option worked great on my Meadowlark Shearwater HRs.