There are three types of bubbles available and they are all gifs at 50x50 pixels. The animated bubbles have a white background.

White Background 00001 - 00010 00011 - 00020 00021 - 00030 00031 - 00040 00041 - 00050

Black Background 00001 - 00010 00011 - 00020 00021 - 00030 00031 - 00040

Animated 00001 - 00010 00011 - 00020 00021 - 00030