I picked up the parts at West Marine, but they are available from many boating supply stores.
The inside track sail stop:
DAVIS INSTRUMENTS Sail Track Stops at West Marine
You can use a dead end bail, but I bought a terminal eye strap and cut off part of the lower plate. I left that part of the strap long enough so it would bridge both sides of the track when tightened down. Depending on size you may find a dead end bail that is ready fit.
FORESPAR Eyestrap at West Marine
All stainless, snug tight fit when clamped and strong enough to securely hold a larger load. Not necessarily a cheap alternative, but I have four of them and I really like the flexibility the track system affords.