Have you dug through the training and continuous improvement documents? Check if there is a budget allocation for “professional certifications” or “membership/subscription to professional institutions”. Those are usually meant for eg. accountants, engineers and other professions that require professional membership. You could try and claim membership to ASCM under that item and it offers discounts in materials and exams.
Regarding which one to do, it depends on what you do and want to do in the future. AFAIK CSCP is a well-rounded curriculum while CPIM mostly revolves around Planning functions.