I home made one by attaching an additional piece of uphaul rope about 2/3 down the normal uphaul. On this extension I tied a stainless steel loop, same sort of diameter as a tennis ball. With a bit of height adjustment I've gotten it about right.
Because I'm using it on a smaller, yet heave, race sail, 5.8 the time for which I can sit back once hooked in to pull up is slightly limited. But it feels really good just pulling on your harness to get the sail out of the water/empty the luff sleeve.
I think official ones are going for 30-40 USD so I decided to build one to give it a go. Definitely worth while on a bigger sail and I can't wait to use it for my 7.5 (also cambered and heavy).
JP Super-X 106l, North F8 Ram: 5.8m,