See RAMBAM Hilchos Sanhedrin, Perek Daled, Halacha Yud Alif. He writes how the Sanhedrin can be established Bizman Hazeh. The RIDVAZ writes that the chachmei Tzfas tried this in the 1500s, and failed (He disagreed with the Chachmei Tzfas). The RAMBAM continues that once the Sanhedrin is established, they can proceed to do all that’s required to re-build the Bais Hamekdash, including determining and appointing a Melech who is a descendant of Bais Dovid, and annointing him with the Shemen Hamishchah, which they will make. Thats the definition of the Mashiach – A melech who is a descendant of Dovid HaMelech and annointed with the Shemen Hamishcha. No Navie is required for any of this according to the RAMBAM. also see Hilchos Bais Habicheerah for how to perform all thats necessary in Yerushalayim. No Navie required.
Menu