What? $50? In any Dutch shop (even supermarkets) you can get good-quality clip-on headlights like those for about EUR 15 per set (or less, if you go for crappy quality)
They run on 2 AAA batteries a piece, come with a holder so you can clip them to your bike but also clip them to your bag or something like that.
They put out a decent amount of light and last long enough - between 5 (bright) and 200 (dim) hours..
You probably can buy them online anywhere.
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