Re: Attaching to ladder...... If you belong to the FMCA, (If you don't give me a few minutes and I can look up the company) there is a plastics company that makes special "Ladder adapters" for the FMCA goose egg These will work just as well for a license plate type sign though you may need to drill a hole or two.... IN THE SIGN. no holes in your lovely rig
There I found it
http://www.kileymold.com/ They make FMCA "plates" and holders and mounts, including one that is specifically designed to hold the FMCA goosegg to a ladder.
NOTE; the Goose egg mounts with two bolts or screws, one at each end, not with 4, like a license plate, so you will either need 2 mounting kits, an egg shaped sign, or drill two holes in the sign.