the oil seems to be available at hobby stores - used in RC car suspensions.
Exactly, for the precision it is silicone oil, it costs much less than that sold by tonearm manufacturers.
Having replaced it in several vintage arms that I own, I can suggest buying the 300,000 / 500,000 cst for a normal descent the 1,000,000 cst for a very very slow descent; beyond that numerical value nothing is found, only fat but not good for the lifter.
Is this: https://i.postimg.cc/g2J8KGYn/IMG-20190831-123401.jpg