If you want a mask that conforms to your, your best bet is to make one. I did this back in sixth grade, so hopefully I remember how to do it.
First, you need petroleum jelly. You also need plaster of paris bandages (aka modroc), something to hold your hair back at the hair line, a bowl of warm water, and a friend.
Use your imagination. I think you know what to do. Pull back your hair with a headband, slather on petroleum jelly, remembering the hairline and eyebrows and such, and let your friend start layering on pieces of the wet bandages. Don't laugh.. or talk... or smile. Let it dry enough to hold its shape and pop it off and then you can fix the holes of the eyes, nose, mouth, whatever with bandages, or you can let it dry completely for a day and go to the fabric store and find some see-through fabric. Attach the fabric by stretching it over the holes and putting bandages around the edges. You can sand down bumpy areas if your friend fucked up. Remember that you can build up the mask wherever you want so you can get rid of features (regular old plaster might be best for that), but don't fuck with the inside where your face goes.
Best way to make a mask (that will fit you... and ONLY you). And relatively cheap.