Techalloy, Natweld, Inweld and others have a nickel 55 tig wire that would work quite well in your app.
Aluminum bronze A2 would also be a good choice if color match is not a problem.
Brazing, by torch or tig, is an alternative as well.
There is a square cast iron rod for torch apps. that works well, too. Does take some heat, though.
Cast iron is funny. What works on todays job may not work tomorrow.
Have a few of these alloys around and use what works best.
if you have questions, let me know!!
Good Luck
brande