Where can I get a new steer tube or 1 1/8" 6061 Aluminum Rod Stock?
2 things: 

While many older forks used replaceable steerer tubes, the steerer tube is still specifically  shaped for that fork. Tubing will not do it. You need an oem replacement steerer tube. Nobody makes forks like that anymore, hence the lack of google results. 

Also, that steerer tube in the photo looks to be steel, and should not be replaced with aluminum.