Cirkuts are a lot of fun and the #6 Outfit is a nice "practical" size, though film can be a bit of a nuisance in that size. A #10 is the nicest Cirkut in actual use and can use 9.5" aerial film without slitting it down, but it is bigger, heavier, and of course much bigger negs and prints - for better or worse.
Gears usually run about $25 each, maybe a bit more now if you get them custom made. I have a lot of extra gears, heads, and other items for #8 and #10. The #6 takes the same gear, but with a slightly longer shaft, so a bit harder to source. The shafts can be replaced, but at that point it might be worth looking into getting the gears custom cut from the start. Ron Klein (a member here) used to do it, but I don't know if he is set up or interested since his move.
Gordon Roth is an amazing older photographer in NJ that might still make gears. I'll ask next time he calls, or can PM with his #. He worked in the Kodak studio in the 50's and knew some of the folks that made the Cirkuts. He also worked in O. Winston Link's studio for a bit. Very interesting to talk to.