It was Elliot Paul Stern (Elliot Stern) who drew attention to the X-Pro2 replacement eye pieces offered by JJC. Here's the link to his blog post:
https://elliotpaulstern.me/2017/04/21/eyecups-compatible-with-fujifilm-x-pro2-jjc/
I have yet to lose the rubber eye piece on my X-Pro2 but I've gone ahead and ordered both offerings made by JJC (EF-XPRO2 and EF-XPRO2G). Purchase is actually made through AliExpress.