I have no idea if it will stand up to shock and vibration of Airstream use, but "Refractory Cement" is available at fireplace shops in tubes. I used it to repair cracks in the molded firebrick floor and walls of my drop-in fireplace at home.
"You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO
2002 Classic 30 Slideout
2001 Safari 25 RB Twin (Gone, but not forgotten)
2013 Dodge 2500 Laramie 4x4 Megacab Cummins
WBCCI 1322, TAC FL-39, AIR 82265