Where to buy speaker stand spikes ?

Thanks Lak. I checked out the site, it has lots of 'points'. At $20-30 a piece, it is a bit on the expensive side. For a set of 8 this could mean over $200, half the price of a decent stand !! Does the improvement in sound quality justify that ? Thanks again for your advice.

Thanks to everyone for the advice. I'm not sure about the option of granite slabs as I have carpeted floor. Just use long bolts is an interesting suggestion, I'll give it a try since it would be the cheapest solution. Thanks again to everyone.