Osmium is in-game already and is mining-only. Decent prices by the standards of "things which are not Painite/core gems", too - you can easily get 35k/tonne for it and it has no real risk of running out of demand.
Palladium has quite interesting in-game economic behaviour, too: it can be mined, of course, but it's also produced in
very small quantities by Extraction economies. Price on the open market is pretty stable at about 13-14k depending on demand, but it sometimes gets used for high-payout "source and return" missions. A couple of years ago, this led to brief bubble-wide Palladium shortages as people tried to buy it up for these missions (and lots of "why can't I find Palladium anywhere this is terrible and Frontier is terrible" threads from players who don't like their trade goods having any sort of dynamic economy behind them). Even now with those missions appearing less frequently, Palladium supplies haven't really recovered. Watch the sharp drop on the supply line in July 3304 as the missions come in (only Colonia markets shown, but the effect in the bubble was similar, if a bit slower due to the bubble economy being much bigger):
(the earlier sharp drop around March 3304 was due to Frontier making Palladium supplies regenerate more slowly as part of the 3.0 update, among many other market tweaks)