It appears the power for the map lights comes from one of the circuit breakers in the panel below the Ford fuse box in your picture.
Here's a link to all the Winnebago online electrical drawings for the 2012 Itasca Sunova 30A.
Table of Contents
The first drawing in the one labeled Front End Wiring Installation" shows the map lights. The large circled area (callout) labeled EA shows where the wiring is run.
If you scroll down to the title block in the lower right corner of the drawing there's a message in a box that reads "FOR ELECTRICAL CALLOUTS SEE DWG NO. 121339-01-000. I didn't look through all the drawings to see if it's included in the online package. If it isn't you can call the Winnebago Service Administration number (1-800-537-1885) and ask for a copy of that drawing to be e mailed, faxed or sent by mail.
Over the years they've e mailed me several detail drawings without hesitation. The detail drawing should give you all the information you need to trace the problem.