Here is what it looks like, posed elegently mext to my vintage NOS Lufkin foldable wooden yardstick:
You could probably make something like it out of a bent peice of steel. The center "bolt" is actually a hollow, internally threaded, sleeve that screws onto the steering post and then you use the nut to tighten down and depress the locking plate via the two "legs" of the device.
By the way, I hope you're kidding about using a bigger hammer. NEVER EVER hit a steering shaft with a hammer, especially the GM shafts. The shafts are actually made of two or three sliding/collapsable sections that are held together with clear/yellow plastic shear-pins that are designed to shatter upon the impact of your face on the wheel. (Ouch!) They are non-repairable if you have hit the shaft and it has collapsed in any way.