You will need a Li-Poly Balance charger so as all 4 cells are balanced properly during charging. R/C Aircraft, cars sites are going to be your best bet. Hobbyking and thr likes.
Glad your getting it sorted, crazy how they sell a psu thats not capable.Bought a Turnigy Accucell 6, good charger but the vendor should know when selling a 6A charger you really need a 6A psu and not the 3A one they supplied, getting sorted, but they're taking their time.