Playing MA Ulm in SP right now, and I've found a ton of recruitable mages. Onyx & Garnet Amazons, Sorceresses, and those hidden Astral mages (stealthy, ethereal, 3S) are all joining my armies. Oh, and some Gnomes.
Forge $%&@, huh? I'll give you a forge $%&@!
Anyway ... I think it's all a matter of luck. The current game is quite unusual for me. In my last game, the best I could find were some Enchantresses and Adepts of the Golden Order, and I controlled about 10x the provinces by the endgame.