There are some decent cheap HID offroad light kits on eBay that are both really effing bright and use less power. Like some people suggest, get some used light enclosures from the junkyard, garage sales or eBay, but get an ebay HID conversion kit.
I got a cheapo dune buggy last year that had headlights but was missing bulbs. I took the opportunity to get a 35w HID conversion kit. Given, the original enclosures are for halogens, but since I'm only gonna need it for trails, not too worried about blinding anyone, and they're REALLY bright while actually using slightly less power. Only problem is that my stupid dune buggy runs the lights directly off the stator, so they're being fed AC current, and they flash like a strobe light! Easy fix, just need to wire them directly to the battery through the key and with a toggle switch.