A participating governmental unit may establish, by law, a separate additional program of interim or supplemental allowances for a class of employees. A participating governmental unit shall fund any additional program of allowances separately from the funding for benefits provided under this Division II. On the written request of a participating governmental unit that desires to establish an additional program authorized under this section, the State Retirement Agency may provide benefit-determination data or other technical assistance. The State Retirement Agency shall charge the participating governmental unit for the expenses of preparing the data or providing the technical assistance.