The one in the picture you posted looks just like a caver's (spelunker's) head light with the head band strap choked up tight. It's got the same look to it with the light assembly able to adjust to any reasonable angle. It may well be that some come with wrist straps for use as shown.
I'm with the others that say the wrist is a poor place to put a light. But if it'll be an ADDITIONAL forward light that goes along with a fixed bar mount then I can't see the harm.