Outside of throwaway lines to demonstrate the ineptness of the Wallace campaign this quite the footnote of history. In fact the only real information comes from an actual footnote in Politics on a Human Scale by Jeff Taylor who apparently corresponded with Sanders in the 1970s.

For some brief context, you should know that Harlan Sanders was a major donor to the Wallace campaign and observers noted that his name got tossed around a lot in the Wallace camp. There isn't a lot of evidence that his being a Vice-Presidential nominee being taken very seriously though he was allegedly short-listed at one point. Other celebrities were considered, such as John Wayne and Paul Harvey, but this was most likely just ideas that were floated and quickly shot down but made for good headlines. Liberty Magazine ran an article about Sanders' name being floated, to which Sanders was apparently quite oblivious until the article's publication. Or at least he feigned ignorance.

In 1975 he stated in a private letter that he had never had any ambition to political office then or now. Sanders viewed himself strictly as a businessman. He would probably have been a bad choice anyway. He was 78 in 1968, and lived in Canada. Some of his personal controversies would have made for more bad press for Wallace. Even more likely is that Sanders had no desire to have his brand associated with the controversial Wallace or to air his own dirty laundry to the press. In the end the only realistic candidates were career politicians who it was hoped would bring moderate voters to Wallace's side.