I bought some headrests from fellow roadster enthusiast Sam Griffin and they arrived today. Sam is a member of the forums at 311s.org, is currently liquidating his 1970 parts car, and is always ready to lend a helping hand.
Funny story: Although he’s a fellow Texan, I found Sam on craigslist San Francisco–he was advertising out there because there are more roadster owners out there and I was searching for parts out there because there are more roadster owners out there. Anyway, he gave me a great deal on a pair of original headrests that will find their way onto the finished car. Thanks Sam!