So, after seeing the geared peg Sanshin, and numerous Traditional Chinese instruments fitted with geared pegs, I always wondered, why hasn’t anyone thought of doing this for Shamisen? I mean, it would be easier to tune, and you wouldn’t have to worry about the tuning peg spinning out of tune. I know on some Chinese Ruan (4 string lute), the pegbox has geared pegs made to look like the traditional style. Why hasn’t anyone tried making a Shamisen like this?
… not only have I thought of that I already did that . . . 
(at least 2 itomaki holes were damaged and needed new reaming which was not possible because of also a crack through one of those holes so it would have needed replacement of wood sections which was beyond my skill and/or wallet so I did consider and eventually go for this untraditional solution and well it looks okay and works)
Shamisen Katoh used to offer something they called “Itomaki that Stay in Place,” and I think they worked with gears. I don’t see anything about it on their website anymore, so maybe it didn’t sell very well. I got to try them out at their shop once, and they seemed to work fine, but Katoh-san also actively discouraged me from getting them. He said he only really recommends them to people who don’t have much strength in their hands, like old people. He also thought it dulled the connection between player and instrument to have something like that in there. Personally, I wouldn’t mind an instrument that stays in tune a little better, but it’s interesting that the option was out there and people didn’t seem to want it that much.
Thanks for the replies. I guess it does exist. xD.