I would just ask the original designer, but after checking their TOS, it appears they don't make alterations after the suit/part is completed. I could be misreading it though. Quote from the TOS "Once the project is in progress, including purchase of materials for the project, the design can not be altered."
Please note this part; (i.e; the head) was not something I commissioned. It was up for auction, someone else bought it, and then eventually offered it up for sale.