Contingent/Contractor/External/Outsource employee can't be seen in Fixed Assets Assignments in R12

When we are going to assign the asset Contingent/Contractor/External/Outsource employee there is only permanent employee showing in list of value, any work around to assign asset to all employees.

Contingent/Contractor/External/Outsource employee use the customer laptop, desktop, Cell phone etc. need to assign the asset but the list of value does not shows external employee