Your work sounds great. There is so little known about the medical efforts and expenses that the company undertook (even if some might say it was to further exploit their worker). These reports appear to exist in a number of mostly research libraries around the country. If you are near one of them or have access to an ILL system, you should be able to get them. Here is where they are located: http://www.worldcat.org/title/annual-report-united-fruit-company-medical-department/oclc/1574308
Please give us an update on how this work goes. When you finish the dissertation, I hope you could share it with us, or at least the relevant chapter.
(Asst. Prof. Soka University of America)