To clarify; Are you looking for a case that has some sort of clear see-though lid closure? Or just a mounting plate that may have about 1.5" of depth?
Seems you're looking for an outline with minimum dimensions of 13" long X 3" tall - maybe 1 to 1.5" deep...does that sound close?
You might be better off soliciting someone to make one using a 3D printer, or make you what you need from wood (then covering it with a fabric)
Or, screw 3 of these together (end to end after cutting off the small protruding mounts that would be in the way)
https://www.amazon.com/Ogrmar-Plasti...NrPXRydWU&th=1