ah, that makes more sense. If they've got the resources, I'm sure they'd figure out a way to find them.
Thing is, I think we're neglecting the concept of snapping. Even for mistings, they've got to snap somewhow. houses like the House Venture would beat their children to make them snap, then test them with all sorts of metals. Allomancers were so valuable that they'd go to great lengths to find them.
Presumably, most of the Seers they found were Nobles. Because the nobility didn't *know* that Seers existed, they wouldn't test their kids for the skill---other metals were much cheaper. Thus the typical seer probably was found by (a) being beaten nearly to death as a kid, snapping, but not knowing it and (b) having the Inquisitors pull one of the raids described above, and instinctively burning Atium.
I would also note that TLR had access to as much Atium as he needed any time he felt he needed it. Its scarcity was somewhat artificial, for good reason. But for little things like finding Seers, I see no difficulty whatsoever in picking up a bit extra for the ministry.