Sections 38.18 to 38.20 shall be supplemental to any existing laws authorizing any town, statutory city, or school district to appropriate funds to aid in the carrying on of any county fair located within the limits of the town, statutory city, or school district, and any town, statutory city, or school district which now has such power shall continue to have such power to make the appropriations to any such county agricultural society as may be authorized by existing laws.