If you do want brass items, Eduard has a nice set prepainted.
It is marketed for the Roden Albatros D.III, but most if not all items can be used for a WnW kit. I have done so several times when doing a wooden hull as you can easily replace all the fuselage inspection panels with pe items and makes using wood-print decals a lot easier and faster.
HGW have also several sets that include fuselage panals, but none with pe seatbelts as far as I know