My bad, did a quick search but with no result myself too. I guess that could well be caused by the unpopularity of 799. Data files for other popular Hickok models can normally be found online with ease.
Hickok is famous for its classic circuit with a #83 and a 5Y3GT, almost all Hickok testers are based upon that particular patented circuit except the ones with solid state rectification, such as 799, which came out pretty late when both tube and tester industry were dying.,