You can get a 70W PSMH ballast and disconnect the X3 lead on the ignitetor to run the lamp. Or, you could purchase this ballast:
https://www.ebay.com/itm/HUBBELL-BAL-0100C-008-BALLAST-KIT-100-WATT-MERCURY-VAPOR-FNOB/183953862130
Thank you! I might ask for it for Christmas.