I take it you mean you would like to ad a bed fly awning ..Length of sail track sealed / riveted across the front lower edge of the roof , Silver poly tarp with sail track edge sewn in and a couple of support poles ropes . [ Cheap version ] ..
Dearer version proper Jayco bag awnings and from memory they still use a sail track across the front lower of the roof .
3rd option a 2m x 2m or 2.5 m Cheapy 4x4 awning [ Kings or the like ] bolted to the roof front panel .