Vicki, if you can't find a higher resolution graphic, you may want to try Vector Magic. I just ran your avatar through it (actually from the other site as avatar slightly larger) and was unsuccessful getting a smooth vector unfortunately, but they have a 'hand-drawn' service, and after answering a few question (how many colors, etc.), it came out as $22 in this case. The results will be far from perfect, but considering the size of the endpoint (an IEM shell) it may work. I've had success in the past using smaller images, turning them into vectors and then blowing them up for posters, etc. Your avatar is pretty small, but at lest it's basic colors and flat.
http://vectormagic.com
Bad example (why you may want to go with the service):