The elastic cord behind the left-side under-seat Easy Reacher pack on my Tour Easy snapped some time ago, probably due to wear against the brace I installed to keep it from flopping around. Quite contrary to what I expected, the repair turned out to be almost trivially easy.
The cord terminates in a pair of plastic lugs, each with a ferrule that slipped off under moderate persuasion to reveal a pair of wedges that engaged the cord:
I expected the ferrule to have a positive lock engaging those wedges, but, nope, there’s (at most) a small ridge. Pry the wedges out and the cord slides out of the lug without a protest; the wedges don’t quite meet in the middle with the ferrule in place and there’s plenty of retention force on that flexy cord.
One of the shorter bungie cords in my collection turned out to be exactly the right diameter and length, with ends secured in its hooks using a simple crimped wire. Bending the ends of the wire at right angles freed the cord from its embrace:
The original stainless steel hook lies by the edge of the road along my usual bicycling route, but a slightly reshaped S hook (made, alas, of ordinary steel) fits around the cord well enough. When this one rusts away, I have plenty more.
Insert cord into lugs, push ferrules over locking wedges, remove one ferrule and lug, install reshaped S hook, reinstall lug and ferrule, install new cord on pack:
Install pack on bike: done!
I have no explanation for how well this worked out; I fear the Universe is saving up spit for something truly awful.