Mo. Rev. Stat. § 61.300: Shall not be sales agent (second, third and fourth class counties).

No county highway engineer, county surveyor or deputy county highway engineer, or deputy county surveyor or road overseer shall be the sales agent, for compensation in the sale to, or purchase by, the state, county or road districts of road tools, culvert or bridge material or machinery, or be pecuniarily interested in any contract for the building of any bridge or culvert or for the improvement of any public road to which the county or any road district is a party.