You're correct in assuming you'd be hard pressed to find a source for lake trout. I saw one listed in Minnesota once but he is no longer listed.

They also like COOOOOOOLLLLLLLLLDDDDDDDDDDDDD water and when water gets into the 50's they want to go deeper to colder water. They are happiest in water that is in the 40's and also shun bright light. I've seen some develop cataracts in raceway hatcheries from sunlight exposure.

If you want lake trout you might as well go with Arctic Char. And lake trout are not know as fast growers but they do have a long lifespan especially in the far north. At least Arctic Char grow faster in fish farm conditions and are less disease prone. If you live in Canada sources for Arctic Char are getting easier and easier to find.

I have lake trout and under 25 inches they seem to quite thin and don't really put on weight until they are quite long.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.