I appreciate that you are looking for a battery powered solution so discard this post from that perspective but since dynamo lights got referred to I thought I would mention that Busch & Muller and Schmidt do dynamo front lights designed to be mounted "upside down."

The Schmidt Edelux II comes with a version which is an upside down mount:



and the Busch & Muller Lumotec IQ-X mounting ring can be turned to mount the light upside down [and it is designed for that purpose].