alternative to speaker stand spikes?

If you are cheap like me, try a nickel. If you are a big spender, you can use quarters. You can also paint them and put stick on furniture glides on the bottom which will allow you to slide the speakers slightly should you need to.

Another good alternative are spike footers. audio advisor is 1 source.

Another inexpensive alternative is to take one of your spikes to the local hardware store and purchase hex bolts or carriage type bolts with same thread dimensions. You can then attach a protective pad if desired. These can be securely fastened to the speakers with the provided nuts. If nuts aren't provided you can purchase them at hardware store. Total cost should be less than $10.
This has worked well for me and my wood floors. I've suggested this several times and am curious if anyone has tried it.

I use and also sell granite slabs for speakers. Although, not the cheapest fix out there, they offer sonic benefits of deeper tighter bass and better soundstage. You can use your spikes but they cannot come in contact with the granite or the midrange might become matalic (I use and would supply custome wood spacers. Now if you are thrifty, I have been told that hockey pucks work just fine on their own (between spikes and wood floor) Good luck

Audiopoints make "Coupling Discs" which protect the floors and other surfaces from the points on spikes.