I did a quick search having seen some nice modern, but retro looking, dynamo lamps from B&M, and the BUSCH + MÜLLER LUMOTEC CLASSIC T SENSO PLUS seems to look great for about $30 to $45 USD. Other various options are available, as well.
See, for instance,
here.
I've seen others that are a bit more like the 'original' on your rat-rod contraption, but the beauty of the rat-rod is that it was older stuff upgraded by the owner...