Port commissions shall adopt, in writing, rules and regulations governing promotional hosting expenditures by port employees or agents. Such rules shall identify officials and agents authorized to make such expenditures and the approved objectives of such spending. Port commissioners shall not personally make such expenditures, or seek reimbursement therefor, except where specific authorization of such expenditures has been approved by the port commission. All payments and reimbursements shall be identified and supported on vouchers approved by the port auditor.