there is nickel and nickel ferrous electrodes and filler wire one is more malleable than the other use the more malleable one as it is less prone to cracking if you choose to actually arc or tig weld it. magna alloys make some very nice rods for cast but they are rather expensive every company has there own blend of cast rods.

for a little job like that it is also worth asking the local engineering shop to weld it for you they have it done while your thinking about it.

Or if you have one of these tools,