PNG ICO ICNS MORE
UI
Pixel
Blueberry
button, radio, off
YellowGreen
32x32
on, button, radio
PNG MORE
Windows 8 Pack (Metro Style)
radio
DarkSlateGray
26x26
Fugue Icons
radio, buttons, ui
Gray
16x16
invisible, radio, button
WhiteSmoke
ui, button, radio
Gnome icons
radio, Form
Black
24x24
Circle, Draw, Form