With the approval of the office of the budget, any state agency may adopt a per diem allowance in lieu of expenses as allowed by section 44-08-04 for its officials and employees whose official duties require that they remain on travel status away from their normal working and living residence for extended periods of time. No per diem allowed may be in excess of the total allowance for meals and lodging as allowed by section 44-08-04. Travel status of one week    or less may not be considered long-term or extended travel. Rental receipts must be used to verify travel status under this section.