Of the cheap headlights I've tried, the best one by far is one of the cheapest, the Xanes XLF-01. You can get it for
$16.60 on Amazon or for
$9.89 on banggood. It might be worth it to pay the extra on Amazon, because you can get a refund if it doesn't work right. I like it so much, I got two. I keep one in my bag as a spare. It makes a beam shape like the one required by German law. It's plenty bright for me. It's tiny and cheap.