I wonder if the thread is dead yet. Seeing that the last reply was in 2010. Anyhow, I think I may have found a possible combination for the wing bow, although I doubt you need it since all the gachas have produced a sufficient amount of them. I found these two in a korean blog, however I'm not too certain of the credibility.
http://blog.naver.com/PostView.nhn?blogId=akqjqp&logNo=120058502951&redirect=Dlog&widgetTypeCall=true
**카실 + 단검 + 채집용단검 = 윙보우
which translates to:
**Kiteshield+ dagger+ gathering dagger = Wingbow
**발톱//채집용단검2+30í¬ì…˜=윙보우
which translates to:
**toenail (no specification)// gathering dagger(2) + 30 potion (my guess is that either 30hp,30sp,30mp) = Wingbow
***I'm not too sure about what // means but my best guess would be that it is an indication that toenail and gathering daggers are interchangeable.
These formulas have not been tested by me.