I have an account and will look up what I can. Can you give me suggestions for search terms. I'm not too familiar with this case but assume he was still unidentified when buried.
ETA: Here's a link to Little Prairie Cemetery in Caruthersville, MO
https://www.findagrave.com/cemetery/29867/little-prairie-cemetery
Also, if it helps, my family recently had a memorial stone (cenotaph) placed at my gr-grandparents grave (it was a smaller stone placed at the foot of their graves). The stone was for my gr-father, their son, who disappeared in the 1930's and was rumored to have been murdered. When I talked to the cemetery, they were very helpful. They said as long as we were family members of the people who were already buried there, it was considered our property and we were free to put another stone there.
Since she's a relative of James Hendricks, the cemetery shouldn't object to having a stone placed there. She would need to check on the regulations of the cemetery for the size and type of stone. Contact the local monument company and they will be familiar with what she needs and what the cemetery wants. The cemetery should have the location for James grave in their records.
https://www.yellowpages.com/caruthersville-mo/mip/little-prairie-cemetery-536092084
Here are YP listings for local monument companies. Looks like the closest are in Dyersburg, TN or Memphis.
https://www.yellowpages.com/search-map/caruthersville-mo/monuments