Noticed this brought up in another post from Northern Europe - Finland.
I took about 5.75 inches of reinforced black 13/16 " (or is it 1/4"?) fuel line and put a spit down the convex side. I slipped this over the edge of the fender such that one end hits the fender strut, the other extends below the speedo cable when the fork is compressed. By splitting the convex side, the curve of the fuel line matches the curve of the fender. Now the cable slides up and down the fuel line and does not touch paint. The reason I used such a long piece is that I had a short piece on there, about 3 inches and it would slide up every once in a while when the speedo cable caught the lower edge. Rather than RTV it (lazy?), or actually work out a "real" length, I tossed what I had, 5.75 inches on there and the strut keeps it from moving around and it works just fine.
The black tubing looks like it was meant to be there.