A few ideas...
1) Brandon fixed a gaiwan lid with some silicone caulk and it worked pretty well. Since the silicone is non toxic and food safe, you could theoretically insert a straw into the spout temporarily, and then build up the wall by shaping the silicone around it. Once it dries, remove the straw, trim the silicone, and then wrap some half-round silver wire
around it for looks. If you did that, you'd probably want to turn the spout into a flat-ended canon style so the wire would wrap around evenly.
2) If you have access to a kiln or jewlers blow torch, you could try using silver clay
to make a cap for the spout. Roll out a sheet, wrap it around, smooth the seams, and trim the excess. I've never worked with this stuff, but have always wanted to give it a try. No guarantees that the pot wouldn't crack. I'd try it though.
3) For a more steampunk look, you could take a food safe metal sheet, wrap it around the spout, and use tiny bolts to hold it on place.
All depends on your mechanical skills.