I can tell you that plugging an Exposure "piggyback" battery into the light will power it.
I suppose if you rigged up a lower voltage battery to the correct connector you may be able to reduce the output from the Redeye. Maybe you can put two batteries into it and then have a switch making them parallel or series - for when you want it megabright or more "sociable". When riding with others I just unplug mine, but you've got me thinking now!!
I met a guy in London one morning who was using a Strada on the front with the remote control. As a result he couldn't use the redeye so had it hooked up to a single cell piggyback. He had the whole thing attached to a quick release saddle bag for quick removal.
Hope that helps,