I've taken hundreds apart, never needed the tool and never damaged anything.
After you have removed the snap ring and the screws holding the housings together bump the side and wiggle the upper housing off. If it doesn't come then place two screwdrivers on either side of the column and pry between the upper and middle housings.
Note: If you are working on the 73 and newer B-body columns they have a spring loaded shaft. when you go to reassemble it the shaft will have pulled itself down and you will need to draw it back out about 1/4 to 1/2" to install the snap ring. The tool you are looking for will not do that. You can probably use the standard GM Steering column depressor tool or what I do is put the nut back on the end of the shaft and pry against it to lift the shaft.
If you want to make that tool you are looking for just get a large washer a small section of pipe and a nut. Make sure the washer is big enough to go around the shaft and drill 3 holes in the washer so it can be screwed to the housing. Next weld teh pipe to the washer and then the nut to the other end of the pipe. Run a bolt in it and it will pull the housing off.