How do you find Uxie?

I found Azelf in Lake Valor but didn't find Uxie in Lake Acuirty Even after I beat the Elite Four a trillion times. GTS is no good either, people wanted to trade Uxie for pokemon like...Darkrai. Shaymin. Arceus. Seriously? Just a Uxie for a really really strong pokemon? I don't understand why people want to be so greedy. Can anybody pls help me solve this question or trade with me over GTS?