Have you tried to find a replacement bushing from a vendor such as Summit Racing or JEGs? Give them the inner (sway bar) measurement, and the outer diameter and width needed, to fit into the brackets you are using.
There are other providers too, but don't go poly for a sway bar bushing. They need to TWIST.
There are other providers too, but don't go poly for a sway bar bushing. They need to TWIST.