Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) narrates: The Prophet (peace and blessings be upon him) said: "Whoever does not find a lower garment (izar) while he is in the state of ihram, and finds trousers, let him wear them; and whoever does not find sandals, let him wear leather socks (khuffs), but let him cut them below the ankles."
Al-Tabarani recorded it in al-Mu'jam al-Awsat, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الحج / 5336