Palladium is just like the other metals, except that it's not as common. You might find it laying around town, buy it from the Consignment store, or drill it up with the Miner. You also might find it while exploring tombs or foreign locations in World Adventures, or buy it from the Relics store.
Once spawned, palladium will be marked on the map when you zoom out to the "map viev", like in WA when you need to find metals, jewels etc. for opportunities.
Change viev to map every sim-day and you should find it. This is the way I've got mine.
This message was edited 1 time. Last update was at 06/10/10 12:56 PM
I got that challenge too. I had to wait a day or two for the palladium to spawn on the map as its not very common, but when it did it had a map pin to locate it with. I found mine in the swamp where the raised rail line goes over it, down near the old rail building.