Hey there DW..how ya going..?
I was thinking you could buy bright red flashing L.E.D. cycling tail lights that come with a clamp and run many hours on double AA batteries. They have several different flashing modes , last many many hours , can be easily mounted with zip ties to the mast , bow, stern etc and are fairly water proof for riding your bike in the rain at night. These should only run between $12 to $18 dollars and can be seen from a long way off.
If you really want some heavy duty spotlight power you could always invest in a Nite Sun H.I.D. (high intensity discharge) or similar brand, front end cycling headlight that is really very bright. These can be mounted to a helmet/headgear or clamped to the handle bars, and really provide some amazing illumination at night
. When two or more people have these on our night rides it make the road seem almost like it was daytime. They are expensive $300 to $500 and would have to be recharged at some point depending on what mode is used..hi-beam--lo-beam..long run..etc but would maybe be of some interest for any night traveling or in the case of the flashing tailights, as an inexpensive safety light during the day. Check your local bike-shop for advice or info.