The specific subject term that you can use to search for results on prisoner labor in Oklahoma is

• Convict Labor -- Oklahoma

The more general subject term is: Convict Labor -- United States
If you do an advanced search for books under these under "subject" in www.worldcat.org (or you local library catalog) - there are several results, which you could look for in your local library or ask them to interlibrary loan for you.

In 1976 an organization called The Prison Industries Reorganization Administration wrote a report called The prison labor problem in Oklahoma: a survey. This is available on two microfiche in a microfiche collection called Crime and juvenile delinquency in which it is item no. PI 17. You could probably obtain this by inter-library loan as well through your local library