My cat didnt come with a tiller that connected to the crossbar so I bought a 4' length of dowling from home depot (forget the thickness, maybe 3/4"), the connector brackets and wrapped it in electrical tape. 4' is borderline too long for me because you have to swing it around the main sheet when you tack or jib. I dont have a trap so I dont think 4' is long enough for you, maybe 6' would do the trick. When I have my feet in the straps and hiked out so my ass is past the side rail, 4' is long enough. Try rigging up something using an extension pole (like the kind you use for painting that retracts inside of itself). I looked into this, but there was too much play, it would have worn out/seized up in no time.
I didnt buy the official hobie tiller not because of price but because my dealer didnt have one and I live in a remote area.
Note: the dowling must have got waterlogged after a year because I was flying a hull and was about to capsize so I let the main out and came crashing down. The force jolted me backwards and I snapped the tiller and fell off the back of the boat. Luckily the boat eventually turned into the wind, meters before smashing into a rock.. I tried to find a better alternative but couldnt, so I made another tiller using the same method as before