Is it permissible to borrow a sum of money, interest-free, from the workplace, to be repaid in monthly installments, in order to cover the remaining costs of Umrah, given that there is a self-contribution to the amount?

There is no harm in borrowing to perform Hajj or Umrah (definition). His Hajj and Umrah are valid, and it is hoped that the repayment of his debt will be facilitated, provided that the loan is interest-free (without usurious interest).