I've started to enchant my weapons and keep needing to recharge them using soul gems. I recently got the soul trap spell so getting souls isnt a problem anymore. However, I'm finding the constant need to get soul gems for enchanted weapons kind of annoying and even more annoying the apparent difficulty and rarity of finding them given how essential they are if your using enchanted weapons. I know you can get them from vendors all over but most of them only have petty or lesser soul gems and the good ones are suuuuper expensive. I've found a few in the wilderness and dungeons, etc. but not that many and the vast majority are petty. So, my question is are there any ways to consistently find high quality soul gems without paying outrageous prices from vendors? (aside from the Black Star daedra quest that I've heard about)
Azura's Star quest, NW of Winterhold. You said besides this quest, but it's really the best way to solve your problem. Without spoiling too much, you can either get it to hold infinate normal souls, or only black (grand) souls. Bandits become your best friend as they're a great source for free grand souls if you go the black soul route.