I'm using a local cabinetmaker, but I did find a few custom options online. CustomMade is a marketplace like etsy. Here is a stand alone file made by a woodworker in MA:
http://www.custommade.com/custom-flat-file/by/Broughtonwoodworks
This is a company that focuses on office cabinetry for architects, etc., but they will do custom files as well:
http://www.smi-products.com/FlatFiles.html
Many thanks Monceau, so nice of you to share the info!