70-76 Demon,Dart sport,Duster Pictorial History

See if you can find any clues to options or optional "packages" that might have included that stripe on the fender tag. I looked at Dante's, Phoenix Graphics and a couple of others. But apparently that particular layout isn't popular or flashy enough to market. However, it may be possible for a good, reputable sign/decal company with pinstriping experience to duplicate and install it for you. But they would need detailed pics & measurements. No idea how much that would cost.

If you don't want to keep it "as produced", there are a lot of optional A-body stripe packages available that you can see on the websites I mentioned. Personally, I always preferred the correct model decals with a car to help minimize confusion. It always bugged me when someone called my Dart Sport a Duster! But that's just me.

I also found this with a image search of 1971 Dodge Demons. 1971 Dodge Demon | GAA Classic Cars
Good luck!