The tube wall thickness would have to be more than 1/16" to reduce it to 1"dia.
I think as said already, you could chop an old 1" steer tube, and weld to a chopped down 1 1/8" fork.
Kastan forks were very similar, lower fork race was 1 1/8, while upper was 1", the steer tube was spliced diagonally to spread load forces and produce a long seem weld. This was in mid 90's i think.