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1) How is the curtain attached to each of the sliders?
2) If you could get the piece off the end of the rail, would you be able to remove the curtain?
3) Can you find another curtain with the sliders already attached?
4) Can you move your sliders to a new curtain?
5) If you can install your sliders into a new curtain, can it be done without removing the sliders from the rail?
To get the "stop" off the end of the rail, you might just drill it out. Then install a stainless nut/bolt, as a new "stop".