A private quarry in the Wheeler Shale of the Utah west desert where you are handed a hammer and put on a face that produces trilobites reliably, mostly Elrathia kingii. Split shale for a few hours and you will leave with a box of them. It is two hours from anywhere on gravel, so fuel up and carry water. Fee by the hour or the day; you keep what you find.
Trilobites · Cambrian, ~500 mya
A commercial or managed site. You pay for access, and what you turn up is yours. Book ahead where the site asks for it.
Other places on the map within a couple of hours.
