Anyone know where one can be found or purchased, am trying to not wear any armor just robes,circlets,gloves and boots, rings,and necklaces, so I'd rather not have to wear the dragon mask with this enchantment.

I have yet to ever see one. The ones I've seen have been unique artifacts.

there IS one necklace that shows up 100% of the time... only trouble is, it's on one of the frozen falmer in cathedral of the forgotten vale. Just a little time consuming...

Radiant Raiment is probably your best bet early in game. Necklaces of Waterbreathing can appear as early as Level 1. The problem is that as you level up, you unlock access to more enchantments in loot and in merchants' inventories, meaning the odds of finding a waterbreathing enchantment goes down.

That's been my experience, too. I have played a few times when I got a Necklace of Waterbreathing early on, and a LOT more playthroughs where I could not find one to save my buttocks

(I like to use Waterbreathing to level my enchanting skill )

And the waterbreathing spell to level up Alteration! (I use that on some characters)

@OP- Do dawnguard or look in clothing shops in solitude.

Um... why the need for the enchanted item in the first place? It's not like there's any area in the game that's going to require you to need one, unless you're a bit scared of the TG quest.

I've swam to pretty far depths without the need of water breathing. Go ahead and practice and time your limit. You can also carry potions (on a shortcut) in case you do run out of breath.

Plus, mage... there's a book for that.