I freely admit this is cheating, and I hope the webmaster doesn't get upset at my giving a plug to another site, but the site below has many RR avatars. Go to the link, then right click the image you want, then select "Copy Link Location". Then, paste the copied link to the source url box on your profile page, and Voila!
(Per the webmaster's recommendation, I have removed the link. E-mail me if you'd like it).
(Per the webmaster's recommendation, I have removed the link. E-mail me if you'd like it).