I was delighted to discover these little USB car chargers on eBay.
I've always thought the 5V regulator would fit into the plug of a car cigarette lighter, saving a bulky unit hanging out of the dashboard.
Finally I found them, and at a great price too! These neat little ones give you 5V out of a USB socket, almost flush with your dashboard!
They arrive in random colours unless specified, I randomly got one in green and one in pink!
Photos of a green one in my retro Astra GTE