I've bought a few antique bottle generators on ebay. They were cheap! Union and Miller and Soubitez are good brands, and I believe they are all out of business now. Some Union generators had the Schwinn name on them. They work well as long as you understand how much drag and noise they make. That generator from Peter White is likely to be nicer, if you're willing to pay the extra.

Most modern LED headlights designed for generators have standlight circuits, so just look for one with that feature. I've tried several B&M lights and one Philips and one Taiwanese brand. I like B&M best.

I don't know of any generator-powered headlight that flashes, unfortunately. If you need flashing, you get it from a battery-powered light.