Firm supply to a specific wip job

We have a certain class of components that are purchased individually for specific wip jobs/customer orders. That same item-A might be on BOM's for 3 different jobs for 3 different customers so we procure them individually for there is paperwork and customer traceability for each item-A. What can we do that in an unconstrained ASCP plan we "hard peg" or allocate PO 123456 to Job 87654 and PO65432 to Job66543?

thanks in advance