The coroner shall be entitled to an allowance of not more than three hundred dollars ($300) per month for expense incurred in and about the performance of the duties of his or her office. The amount of the allowance shall be determined by the county governing body and shall be paid at the end of each month from any funds in the county treasury not otherwise appropriated. The allowance shall be in addition to all compensation, fees, and allowances heretofore provided by law.