Most of the ones I've seen have been pretty rough too. These things are almost impossible to find NOS; the only pair I've ever seen went for big bucks on eBay.
If the sleeves are scuffed up but otherwise intact, I've had good luck sanding and painting them semi-gloss black. If some spots are worn away, painting them and the shock bodies above the adjuster black can help for non-restoration applications.
I've always wondered how 2" heat-shrink tubing on top of the guides would work. It should allow the 'scrape bars' molded into the plastic to show through at least a little, and will obviously cover any holes or missing pieces. Glossy-finish black 2:1 tubing with adhesive would be ideal, but I couldn't find it in 2" (I only looked for about 10 minutes, though). The place below has a good assortment:
http://cableorganizer.com/heat-shrink/heat-shrink2.htmIf someone took the time to reproduce these things, I bet they'd sell a ton of them, at least for a while. I'd probably get 5 pairs myself, if the price was right.
Ray