Keystone uses a 4" round incandesent sealed light for both the red brake/turn/tail light and another for the back up light with a clear lens. I have been looking on line for these since they are not readily available from the RV stores or dealers. I had to wait 12 days to have a replacement ordered and delivered.
My hope in finding them online was to get them at a reduced price. Not so. Command Electronics retails them online for double what the dealer charged me for it. But if you want to look, you can find the replacement at
http://www.commandelectronics.com/in...il-lights.html. The part number is Command #003-5300C for the backup and #003-5300R for the tail light. Command retails them for $15.95 each, but my dealer charged me $7.95 + tax.
I found some 4" round LED tail/brake/turn lights online for just under $30.00 each.