The threaded rod the gizmo is based on is the same thread as the top of most tripods (3/8 16)....

Painting the thing black is optional. I also ground down the tip to a blunt pencil-point.

Watch the level as you press in the spike.

Total cost: $19.77, with parts left over.  It would have been $17, but Home Depot was out of the two-pack of couplers so I had to get 5. The couplers can be found by the nuts and bolts AND in the electrical department.

This is the finished product. The reason there are so many levels of washers is that you need a place to lift the spike out and press it in. You really don't want to push down and pull up on the camera - it takes some force to bury the spike and yank it out.

It's pretty simple to build - the only "work" is cutting the rod to length. I made two rods - a one foot length and a three foot length.  You may also have to sand the ends smooth and run a nut over the threads to remove any burrs.

The rubber washer sits atop the entire contraption and gets sandwiched between the pano head and fender washer.  This way the pano head won't bind to the rod.

All the nuts are tightened and locked as much as possible.  I decided not to use any lock washers and they are really not needed.

I left 3/8" of threads exposed above the rubber washer.

I painted mine black - the top fender washer and rubber washer were removed for this.  I painted the top fender washer separately.

If you wish, you can use another coupling to lengthen the rod. This can be used as a tripod extension.  Alternately you can just make the two foot long remaining section a tripod extension.

I prefer the latter because it's cleaner (those threads get full of dirt!) The tripod extension only requires the top level of fender washer and rubber washer.

Here you see the reason for the multiple levels of washers.

Finger Spaces!

Note on use: The ENTIRE spike WILL turn unless you grab the finger holds while rotating the pano head.  You could weld or bolt a cross piece to it to prevent this.  At first I gripped the finger holds to prevent the spike from turning.  Later I let it turn and watched the rotation. Close is often good enough (especially since I shoot six images.)