Made with :
- the cap of an insecticide spray (those used for black beetles). Ext.dia.56 mm,
- a 52 mm filter which glass is removed (just keep the mounting frame),
- neoprene glue,
- the removable S2IS' tube,
- a piece of motorcycle inner tube (dia.50 mm).

1/ Remove the glass of the filter frame.
2/ After it is removed, file the inner groove in the frame.
3/ Cut the bottom of the spray cap at 42 mm of the opening
      (Use a tape to guide the cutter).
4/ Glue the filter frame (male threads inside) with the neoprene glue, to the cut side of the cap.
      Don't wait as usual before assembling because it won't be possible
      to correctly engage the filter frame into the cap.
      2 hrs curing at least.
5/ The S2IS tube fits without clearance into the cap. So it doesn't needs additional gluing.
      The small dents in the plastic cap are enough.
      It is important not to use glue just in case you need it for further use.
6/ Cut a piece of rubber inner tube slightly longer than the cap.
      Adjust it with the cutter it when in place.

Mount the adapter tube you made onto your camera.
Screw the 52 mm dia lens on the adapter (Raynox DCR6600-PRO in this example).
That's all.

The plastic cap becomes rather stiff when everything is assembled.
The rubber of the inner tube plays two roles:
- it ensures a correct grip for a good handling and
- it avoids the light penetration.

When the lens isn't mounted on the camera, it's possible
to put a 52 mm UV filter at the end in order to protect the camera lens.
The guy prefers to keep the adapter tube mounted for protection purpose.
He grouses about the Canon lens cap ...

I don't have a new Canon lens cap, what a pity ! :-)