Google has added the ability for Super-Admins to manage their own storage. To add additional storage to a user's account, please follow the directions at the following link, or follow the instructions listed below: https://support.google.com/a/answer/1727173?hl=en 

  1. Sign in to the Google Admin console.
  2. From the dashboard, click Billing.

    The Billing page lists each product you've purchased, along with basic information about your subscription.

  3. Click three vertical dots next to the drive product and select Manage Licenses.
  4. On the license management page, do the following:
  5. Click the Unassigned users tab.
  6. Check the box next to each user you want to assign a license to.
  7. Click the Assign button and choose the license option you want from the drop-list that appears. The list also shows the number of licenses you've purchased and the number that are already in use.

    This assigns a license to each selected user and moves them from the Unassigned users tab to the Assigned users tab.

    Additional storage may take up to 24 hours to be reflected in the account.