If the curves are gradual, quarter round may be flexible enough to be suitable. There are also some PVC trim products (including some with woodgrain appliques that very closely match the honey oak veneer or applique of my RV's cabinetry) that are incidentally more flexy than actual wood.
If you want lighting, maybe a series of some of
these with the corresponding LED strips would be the ticket.
You might be able to do some sort of upholstery around a core of some sort (a strip of luan would probably suffice) held on with e.g. screws and snap buttons or something like that. With a little bit of padding, it could follow the contours where things aren't precisely straight and flat.