I use the XS Foto Panorama Mask.
GoMask Panorama | XS Foto
While a little expensive, there's a lot to love about it. The silicone skirt is super soft and forms a ridiculously tight seal. It's very low profile and I really like the panoramic glass. It truly opens the field of view. They have other options if you don't want the panoramic mask. In terms of camera mounting, what makes this mask superior to others is the camera mounting posts are stainless steel and molded into the frame. The side post is also tapped so the mounting screw threads directly to the post eliminating the potential of losing the nut on typical camera mounts. Also, because it's metal you can really wrench it down tight eliminating a common problem with plastic mounts where the camera will tilt and ruin the footage. That typically happens when jumping into the water. Finally, I thought their strap would be a bit gimmicky, but it turns out that it works great for easy loosening and tightening and also serves as a nice back of the head cushion if you whip your head back too far and your first stage is sitting high.