Ok, after searching around a bit, I found this which I think I'm going to order:

12v 5.0 Ah NiMH battery pack + Smart charger ($59.95)

That should solve my battery and charger needs. The batteries in the pack are C cells, but 5.0 Ah should give me about 90 minutes of runtime at 40 watts, which is acceptable. The size of the pack should fit nicely into a water bottle, which should waterproof everything. The charger is supposed to recharge in 3 hours.

With $5.72 (plus shipping) for the two bulbs I posted the link for earlier, this should turn my EVO dual into a pretty kicka$$ lighting setup.

This will bring my total price to about $170, not counting shipping. If all works as planned, I think it will be pretty hard to beat this setup for the price. From what I've heard, a flood paired with a spot is a pretty good combination. The spot gives you max light where you need it, and the flood fills in the periphery while softening the contrast of the spot. If I want a backup battery, the 6v battery pack that came with the lights would work as a backup to the 12v battery. I'll have to see how that goes, I don't think I'll really need a backup. I'll post an update once I get it all running.