A district may insure its directors, officers, assistants, employees, agents, and deputies for injury, death, or disability incurred while engaged in the business of the district and the cost of such insurance is a proper charge against the district. Such insurance is in addition to any compensation secured under the provisions of Division 4 (commencing with Section 3201) of the Labor Code and inuring to the benefit of the director, officer, deputy, assistant, employee, or agent, or his beneficiary or heir.