If the rest of the door is good, it would be possible to cut out the damaged part and weld in a patch panel. I have some hold hoods around for making patches where panels aren't available. I cut a rectangle large enough to cover the damage, then use the patch to mark a hole to cut. I use a nibbler to cut the hole and an electric shear to cut the patch. I would examine the whole door. There is a good chance that it has more damage than you think. There are doors around to be found.
