9mm and 1/8" and log... If it's a new design for mfg. maybe you can have them made. If it's a proto for you, surplus? All minor barriers to leap.
Newark/Farnell has pretty good search filters (not recommended for Android phone!) that work pretty well on a computer, but I didn't find (quickly) diameter. 10 k log with 1/8" shaft did come up (I didn't check IN STOCK box), but ignore the picture which had a disclaimer as well as showing a 1/4" shaft. Then I saw there seemed to be more options with 3.17 mm diameter shaft options than 1/8". I find weirder combos and specials there, but really stupid typos...many capacitors listed as F instead of uF, and wrong datasheets delivered from library. But the inventory and pricing has made it worth my while to push past the occasional misinfo. Nah...only found 11mm and 1/2" body with 3.18mm shaft diameter today...and pricey.
Bourns PTV09 series has listed 18 different tapers, and 9 mm diameter...but apparently not 1/8" shaft. 3310 series looks like a trimpot with a bushing added...so I'd check the rotational life rating...but linear only.
https://www.potentiometers.com/select_Bourns.cfm
I see others in MOD POT series but they are 5/8" square.
I keep finding solder-lug (not PC) CTS(EIA137) pots in my garage and basement with no value marked...I can never remember whether they were 10k or 100k because when I measure one, it's the 'other' value than what I was looking for that time...don't think I ever found one that wasn't linear. Weird long 1/8" brass shaft with about 50% diameter reduction flat...always made a mental note 'gotta hacksaw THAT off!'. I don't remember last place I saw them. I think there was a box originally in the 90's but they migrate for projects.
Hopefully that's not totally unhelpful...
Dimensionally restrictive requirement perhaps?
I always find myself thinking up creative ways to use accumulated inventory (no, not a hoarder...just can't find the things I have).
Murray
