Build your own concrete shower pan -- it isn't nearly as hard as you might think!
DIY Walk-In Shower: Step 3- Prep For Tile - DIYdiva
DIY Bathroom Renovation: How to Build a Custom Tiled Shower Pan — Apartment Therapy Tutorials
How to pour a shower pan - great website
Bathroom with pale grey brick tiles
How to waterproof and tile walk-in tile shower DIY- step by step instructions - part "1" of 2 - YouTube
http://www.rvmaintenanceoptions.com/rvshowerpans.php has some information on shopping for a new shower pan for a RV.
How To Build A Shower Pan And Guides ~ http://lanewstalk.com/tricks-how-to-build-shower-pan/
shower pan? Curbless shower with a linear drain at the door ~ http://walkinshowers.org/best-shower-drain-reviews.html
How to Build a Shower Pan