Joined: Aug 2010
Posts: 12,747
Likes: 2,108
From: Madison, WI
Bikes: 1961 Ideor, 1966 Perfekt 3 Speed AB Hub, 1994 Bridgestone MB-6, 2006 Airnimal Joey, 2009 Thorn Sherpa, 2013 Thorn Nomad MkII, 2015 VO Pass Hunter, 2017 Lynskey Backroad, 2017 Raleigh Gran Prix, 1980s Bianchi Mixte on a trainer. Others are now gone.
Agree with Robow, you are very unlikely to find a welder that could fix a bike frame by welding it.
But if it is a steel frame or fork, you might find someone that can make a very ugly repair with brazing on some extra steel as a reinforcement over the crack or by fillet brazing. But that would be an emergency repair to get you someplace where you could get another frame or fork. In that case, they would provide the brazing materials, you would not carry anything for the repair.
Where are you planning to go that this would be a concern?