Thinking more about a badge...
Not only would it help those S4ME folks to meet up who want to, but people wearing it would be a good advert for the site - and of course there'll be lots of researchers there, which is an audience we want to reach.
So here's the S4ME logo, with the web address added below and room at the top to stick a safety pin through it to attach it to your clothes, if you print it off.
If you want to make it stand out a bit more, you could always leave a bit of a margin of white paper around it when you cut it out.
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