been ages since i done it (3 year) it isnt exactly a shop your looking for its hades you can find him in memoria in the under water part he is behind some scenery just go behind scenery and keep hitting x eventually you will find him then you will have to do a fight (i think you fight hades) then after that just go back to same place an he will synth stuff for you

like i said been about 3 year since i done it but i think the info i have given seems about right