TUSA offer a great selection of prescription lenses for their masks. The masks are great too! These are made to fit the lenses perfectly and replace the glass, rather than just a stick on lens. I believe Mares also offer a good range of lenses.
Never seen any lenses for the Shadow. Most prescription lenses are for dual lens masks not single lens.TUSA lenses are about $49 for each side, and come in plus or minus depending on your vision needs.
Don't feel like replacing my Oceanic SHADOW if I can help it....
I've gotten these for some of my dive friendshttp://optx2020.com/p-23-hydrotac-diveoptx-stick-on-lenses-for-divers-large.aspxThe general feedback is they're ok. Though some have highlighted that with the stick on lens, it's harder to clean your mask with baby shampoo
There is hope ... try this DIY using Daiso specs, carefully drill 2 holes, thread thru bungee cord, secure to mask strap. $3It works ! Recently tried out in Bali. My wife has both lenses while I only use 1. When not in macro mode, simply pull it over your head.Patent Pending