I would buy any from the big names. Facnor, Karver, Selden, Profurl,
Harken, etc.
Go to youtube watch the videos. You become competent top down
furler in 15 minutes or so.
BTW Purpose built
sails work best.
Best thing since sliced bread when it comes to shorthanded handling any kite bigger than say 600 ft sq.
PS There are models that can be shared with C0 style
sails - you just add the
furling cable and a different tack swivel and you have a 2 in 1 system for way less than twice the
price.
b.