Someone in the Virtual Boy Fans Unite group on facebook said his lenses were cracked.  I didnt have any extras to send, so within an hour I'd removed the best original lens I had from one of my two working Virtual Boys, and I reverse engineered the lens in cad.  I then printed out a prototype and tested for fit (prototype in PETG shown in pictures)

These should work great when printed in crystal clear resin and then tinted red.  It may be difficult to get an exact match but then again I'm not really sure how much that matters.  The part should be oriented on the build plate in a way to minimize the appearence of layer lines or voxel lines across the part of the lens you look through.  That means either printing it with that part of it face down, or orienting it so that this part is straight vertical.  

Another idea is remixing this file so that the end user can simply glue a piece of red acrylic in place of the flat part of the lens.  The important thing is that now theres a convenient starting point for a whole world of possibilites.  I've also Included the fusion 360 file, and the model exported in a .step file format just in case.