I use an AD (anti-droplet mask), it's like the loose fitting one you mention. This doesn't filter incoming or outgoing air, but mostly viruses travel in droplets of water and this will prevent any direct contact. But the key is I don't mind wearing it all day if I have to.

The longest Highspeed trail journeys here are like 3 hours. at 300km/hr, 10 hours gets you a long distance, unless the thing is stopping a lot.