I know this post is a little old, but what the hay
I have been making padlock lock shims for quite sometime now, the alum can trick never ever worked for me so I shopped around.
I picked up a budget retractable tape measure and sanded the paint along with all the measuremnts of with a 240ish grit emery paper.
I cut out a template similer to the commercial shim but with longer handles for better grip.
The cut out shims where then cleaned up on the edges, especially on junction cuts.
I placed duct tape on the outside of the handle, and formed the shim around a padlock shackle.
These shims work great, are cheap as chips, take bugger all to make and can be used a few times if your lucky.
i dont know how to post pics yet, but in the future I'll show you what i mean.

The Only Thing That Counts is Making Entry.
Mitch, Auckland, New Zealand, Method-of-Entry