Adept I spells are loot drops. They aren't particularly rare drops but, with so many classes that are spellcasters, the odds of a given spell you need dropping and then you winning the lotto for it are pretty small. As with many things, you're better off checking the Broker for player-sold spells that you need. Trust someone else's luck to have what you're looking for.
The one drawback to Adept spells that I've seen are that you fizzle them a distressingly high percentage of the time- much higher than Apps, no matter if they're APP I, II or III. On the good side, as your skill in that spell-type rises, you do fizzle less, even if still more often than you do Apps.
I did see one Master I spell for same on Najena. I think it was priced at 35gp or so....