I'm not sure the epoxy would retain the cable over the ball.
Short term I'd imagine even a rubber band fitted over the ball before the cable end was fitted & then wrapped over the cable end might work.
Your idea of buying another cable to get the retaining clip would work, but would be an expensive solution I think. The clips are removable - as you've found - lol.
A second hand part would be ideal if you can find one.
On many Land Rovers, gas struts are used to control the opening of tailgates & bonnets & they all use the same sort of clip to retain them to a ball joint as your cable. They're often replaced as the gas strut leaks & loses pressure - creating a spring clip that you need & a scrap gas strut.
Can you measure the bit of the cable end area where the clip should fit over ?
If its approx 15mm across, I have a couple of redundant clip off struts I've removed (but still have due to a hoarding problem - lol)
You can have them if you want.