DR500S cable should work. DR forks are only about 12mm longer so length will be much the same. Most other RM/PE forks are longer so you could have issues with extra cable length not needed so thats why i sugest the DR500S cable. You will need to check the front brake plate. Does the adjuster thread in or just slip in? You may need to use a 78 or 79 PE250 front brake plate or maybe even a 79-82 TS250 brake plate. they are all much the same, still have under slung speedo drive, its just there is a difference with the way the cable is retained to the brake plate. I got a box full of plates and i could check for you. Another option SP370 78/79 cable.