There is a photo of the tombstone of George F. O'Brien on usgwtombstones.org. (click state projects, click Michigan, click Charlevoix county).
He is buried in Brookside Cemetery in Charlevoix County.
I don't know if it is your George F., but it's worth looking at. Hope that helps.
That website is great for looking for tombstone photos. You can also check out seekingmichigan.org and use the advanced search function to find Michigan death certificates from 1897-1920.
Beal City, Michigan