I think the troubles that you were running in to with resizing the animated image that you found was that the formatting for multiple images tends to get lost when it's resized. That being said, I was able to resize it for you, it's the right size for your avatar, but the file size is too large, so I don't think it'll work here.
Here is what I came up with, using the 4 pics that you sent me. I had to make it a little bit smaller than the 100X100 allowed (it's 86X64) so that I could still use all 4 pics and stay within the 20KB file size limit.
Hope this works for you