A rubber band would make a horrible anti-static strap. If you really want one, they can be had for about $10 USD.
That said, static electricity damage isn't as common as some make it sound. In all of my builds, I just take some basic precautions and I'm good.
Don't pet the cat or dog and immediately work on/touch the electronics or PC components.
Don't drag your feet on the carpets.
etc.
I usually try to work where there is no carpet to prevent that part.
Touch the chassis before moving components into it (to bring it to the same level)
Work in an area with decent humidity.
Simple stuff that won't cost you a dime