Sanballat is found in the book of Nehemiah 10 times.

The Elephantine Papyri
The Elephantine Papyri is a collection of ancient Jewish manuscripts dating from the fifth century BC. They come from a Jewish community at Elephantine, the island in the Nile at the border of Nubia. The ‘Passover letter’ of 419 BCE (discovered in 1907), which gives detailed instructions for properly keeping Passover is in the Egyptian Museum of Berlin. Further Elephantine papyri are at the Brooklyn Museum. The discovery of the Brooklyn papyri is a remarkable story itself. The documents were first acquired in 1893 by New York journalist Charles Edwin Wilbour. After lying in a warehouse for more than 50 years, the papyri were shipped to the Egyptian Department of the Brooklyn Museum. It was at this time that scholars finally realized that “Wilbour had acquired the first Elephantine papyri”. The papyri are reported to confirm the account found in the biblical books of Ezra and Nehemiah, specifically mentioning two people in mentioned in the book of Nehemiah, Sanballat the Horonite and Johanan, Neh. 2:19, 12:23 (Merrill Unger, Unger’s Bible Handbook, p.260).

Translation:
“ We have also set forth the whole matter in a letter in our name to Delaiah and Shelemiah, the sons of Sanballat, the governor of Samaria. Furthermore, Arsames (the Persian satrap) knew nothing of all that was perpetrated on us. On the twentieth of Marheshwan, the seventeenth year of Darius the King. “

The full translation of the letter that contains Sanballat’s name

Scriptures
Nehemiah 4:1 But it came to pass, that when Sanballat heard that we builded the wall, he was wroth, and took great indignation, and mocked the Jews.