Use stainless steel bolts, washers, and nuts to do your repair. Any kind of high temp welding epoxy is going to introduce some kind of chemical into your cooks.
I would advise against actual welding as well unless the kettle is in exceptionally poor condition or you have someone with some exceptional pinpoint skills to do the welding. Generally welding will cause more porcelain to pop.
Sent from my SM-G981U using
Weber Kettle Club mobile app