I've been getting most of my Walkera parts, for Master CP and Genius CP, from eBay sellers; "emilyandlily", "ujtoys", and "walkera-esky" (also known as "RCCarMax" direct internet store). Also BangGood has a good selection and great prices, if you can wait for shipments from China. I'll recommend all of these.
And I have accumulated considerable experience in ordering replacement parts and installing - thank Walkera for making Master CP parts affordable and fairly easily replaced.
As for WOW hobbies, I have second thoughts. I think they may have sent me a Master CP, supposedly 'checked out', that had a stripped servo - but since I was completely new to CP helis, it took me months to realize what MAY have been my initial problem. (With training gear attached, it tilted to the right BEFORE I could make lift-off, until the blades made ground contact due to the tilt - even with heavy left aileron input, and with a curious ticky-ticky sound from a servo without any command input whenever the battery was connected. With all the warnings on the forums that CP was TOTALLY different than FP, I just thought I was doing something wrong. Finally replaced all three servos and the heli behaved as I expected from my FP experience - except a lot more sensitive and fast. Removed the training gear when the heli started oscillating with increasing amplitude in a hover without any control input.) But I have no proof, so don't rule out WOW hobbies on my suspicions, just comparison shop the prices from all these sources.