4lvl wings are only available in webshop. You cant make them.
What u also whant to know:
1) 4lvl wings dont have a class restriction. Eg. a BM, MG, ELF can wear them. Not sure about Summoner and DL tho.
2) IMPORTANT. The 4lvl wings are non tradable and non upgradable. Meaning if you buy them F.O but +0 they will stay like that.
3) 4lvl wings are NON TRADABLE. You cannot show or trade them. Only way to swap wings from char to char is frou deposit.
So to renember. If u buy wings buy em +15+7%(about 8k credits from what i renember)
That should answer all your questions.