Anyone have any suggestions for a low cost tying light for use where electricity is not available?

I'm looking for a light to use while tying "on the road". It will have to be battery operated. It will also need to be portable and somewhat small.

I have good lights at home, so it will not be used very much. So, I want to keep the cost as low as possible. But it has to be below $50.

Does such a light exist?