Here are a few to get you started.
Ehobby asia. These guys kinda knuckle drag when it comes to shipping your item but they do usually get it out with in 4-5 days of your payment.
Ebaybanned. I personally dont use them because they are usually extremely slow to ship an item and its been noted that they sometimes have crap communication. Worst comes to worst you file a pay pal claim if they screw you over. However they do have free shipping. I guess you get what you pay for.
Theres RSOV. Even though the majority of what they sell is low end garbage they do have the style of mask you are looking for. Their shipping can be somewhat expensive.
There is airsoft global. I usually have great communication with them, and they do ship the item very quickly. Shipping can be expensive depending on what you choose.
All these retailers are based in asia and they were all googled for you in under 2 minutes.