I'm using the stock lights as lows and I have a large set of trailtechs for Hi's. The only reason I did this was for other people's concern. The HID's are killer to look at. So I can use the stockers when riding past another person.
Sorry, More to answer your question. Your biggest problem with finding aftermarket lighting is most lighting is 55 watts per bulb. Which is fine if your going to use a single light. But running both will harm your quad being your quad only puts out 100watts max. You'd also have to leave some overhead for bulb startup and running your electical system.
rocky mountain atv, its actually a 250watt, i dont know what I was thinkning, runs about 200bucks. I was planning to add lights to run the trails at speed, but ended up wrecking my bike and to make a long story short snapped a front shock... upgraded to ohlins and found that the stock lights no longer fit with the resis. so I was in need of a light fast and went with automotive hids. I miss the wide beams though.