What is a good replacement for a cable end cap?
Those end-caps are quite reusable. If you take a pair of pliers and squeeze it gently so that the flattened portion opens up you can then slide it back onto the cable. Using the pliers you can then re-crimp it on the cable. Although it looks ugly and everyone will know that you are too cheap to buy a 10c end-cap.

A little bit of superglue placed at the end of the cut seems to help keep the individual wires from separating.