Somewhere hidden in the darkest depths of the universe is a drawer filled with odd socks, biro pens, screwdriver bits and lost rubber feet from microphone stands.
A microphone stand with missing feet is a terrible thing - amongst a multitude of other sins, it will surely tarnish the varnish on your studio's glorious wooden floor.
Fortunately the answer is here for pennies. Buy as many as you need then some more, for ye will surely need them again.