Best online shops to find details for an ALW Phantom costume?

There are no pre-made, mass produced Phantom costumes that do not look like crap. bạn will have to assemble yourself, hoặc commission a seamstress to get what bạn want.
I'm afraid your câu hỏi wasn't entirely clear, as well. Are bạn looking for a good ALW style costume (and then bạn need to specify stage hoặc movie), hoặc thêm Leroux? In the case of the stage style costume I know Phantom On A Budget offers tips to get the right look. Although, for the sequined cloak, you're going to either have to commission it hoặc get yourself a Bedazzler.
If you're wanting thêm of a Leroux, then I would go on ebay to look for gentleman's styles from the late 1800s. The novel đã đưa ý kiến that he dressed in evening attire (so very elegant and fashionable), that his suit was ill-fitting, and he wore a black full face mask. If bạn want something fancy, Venetian masks can be found. Papier mache would be period appropriate, hoặc bạn could do what I did and make your own (mine looks like s**t, but it was a first attempt and it's still kinda cool
Goodwill and other một giây hand hoặc retro stores will also be your friends.
Other than that, throw me some specifics on what bạn want and I can give bạn thêm detail.