Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) narrates that he saw the Prophet (peace and blessings be upon him) urinating while standing.
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains a narrator, Ibrahim bin Hammad bin Abi Hazim, and I have not seen anyone who mentions him.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1016