Duh... There's a binding post screw that keeps the cable from slipping so, don't worry about the end caps having to fix the cable.
The purpose of the end cap is to prevent the cable from fraying.
Don't go to a chandlery for marine hardware - its much too heavy and probably too big for the cable.
Instead, try one these 3 things;
1) Go to bike store and ask for end cap. Usually free... Crimp it on with any old pair of pliers
2) Dip the end cable in a little epoxy of super glues (this is what I do).
3) Use a benzo torch to cut the cable or, even melt the end (My local bike shop does this -very slick!).