The exposition of GNS theory itself denies that a "pure" game of any of those is possible while still being a roleplaying game, but we can easily talk about simulation-heavy games, even if we can't talk about "pure" Simulationist games.
From the gist of this question as I understand it, you're just puzzled that you can find strong examples of only Gamist and Narrativist games, and you only really need one example to be satisfied that exemplars of heavy Simulationism exist generally.
For the one counter-example I would offer HârnMaster in any of its editions. Concerned with simulating a medieval-like world, it dispenses significantly with balance among characters or "encounters", and its mechanics are not built to emulate a narrative structure, leaving it low on Gamist and Narrativist scales and high on the Simulationist scale.
Simulationist games are rare in practice because it takes quite a strong commitment and taste for simulation to enjoy a game that tries so much to not be very game-y. It takes significant intestinal fortitude, so to speak, to put up with a first play session that entirely involves being a hapless serf wandering alone in the forest after fleeing your lord's lands and then dying to blood loss from a wolf tearing open your leg, and to put up with it enough to actually enjoy the immersion of that hardcore degree of simulation. Such gamers exist (hi!), but those who can enjoy Simulation to the near exclusion of Gamist and Narrative controls on events are few enough that they're not often catered to.
Besides, doing Simulationism well is the first "tech level," if you will, in the development of RPG design history, so such gamers are already well-served by existing games. So that's another reason you're having a hard time finding them: the majority if them are old games, with few improvements left to make that their audience would care for.
Rob Conley has written an extensive Actual Play post on a session of HârnMaster that is a good example of what a Simulationist game ends up being like. There is a lot randomly generating character details in order to create a character that has a background and starting features that are statistically realistic in the setting (such as having an allergy to shellfish, being born of low stock, having been enslaved, or lamed at a young age). Play involves a lot of "slice of life" detail that makes the world feel like a real place. Of particular note on the Simulationism/Gamism difference, note the nature of the cave in that play report: no smooth floors and interconnected passages on a consistent level as a way of making caves convenient for gameplay reasons – instead, it's like a real cave, with frustratingly fractured terrain that barely qualifies as a floor, difficult squeezes, and the rare flat area that's inhabitable. Note the way combat works, too: it's all about injuries, shock, passing out from pain, playing to your strengths when you can, and suffering the turns of random luck when you're not playing to your advantages. There is heroism there; but it's small, hard-won and not taken for granted, much like a hero you'd read about on the local news is a hero for having good luck at the right time and place when they could have as easily ended up a victim.
A final note.
This answer starts by taking GNS theory as a given and works inside that framework to help explain it. In reality, GNS has a lot of holes and problems – enough so that it's largely considered flawed and obsolete, even by its creator Ron Edwards. However, its replacement, the Big Model, is a many-tentacled beast that is hard to get a mental grip on, and it still uses the fundamental concept of a threefold division in major play styles (and so doesn't thoroughly repudiate the GNS way of thinking about roleplaying), so in practice it hasn't supplanted GNS theory in the popular discourse. The Big Model does attempt to address the discrepancies that people are pointing out in how GNS gets (mis)used, though – the quibbles with me calling a game "Simulationist" are entirely fair. Still, it will be some years or decades before we can expect talk of "Simulationist games" to fade away and be replaced by talk of designers who mechanically support a "right to dream" play agenda.