I have a 2014 C-Max Hybrid Energi and went to my local yard (Tear-a-Part in Salt Lake City) and got a donut from a 2018 Ford Focus. I also got a lug nut wrench and jack, all for $31.00. Also, the interchange search results they printed up for me list any Focus from 2012-2018 as a match for any C-max from 2013-2018. Hope that helps anyone else out there looking to add a spare!