Right now, my setup is: One 20-watt MR-11 narrow spot (which is engineered to perform like a 35-watt, all I can say is, "Wow,") my yellow xenon strobe strapped upside-down under my seat (identical to those you hear about in this thread, cost me about $8,) powered by a 3.4 AH lead-acid battery. The 3.4 fits neatly into my old Vistalight battery pouch. And of course, a fuse.

Gives me a little more than an hour's run-time. I'll probably have to go with a 5 AH battery next time, since smaller batteries lose capacity more quickly.