Rare as rocking horse crap those long chain sliders,just couldn't purchase one for love or money,and was advised to use a standard one fixed in the usual place with the bolt at the rear end (hub) & the front silcone down into position,mines still in play after 2 seasons on the roads.
Guess you've already answered your own question: Maybe someone could make a CAD drawing of these and have them 3D printed in nylon or something?
What seven times plus more money than the standard ones,when they're only consumables...but i must say i do like your second idea.
Febur sell them new made from some machine nylon its quite tough stuff. Jhp can supply them I've two sets off them myself.
