You're never going to get anywhere remotely near wholesale prices, honestly.
I would just buy a whole wrecked Leaf, strip the pack out and sell the rest for scrap. You'll get OEM quality batteries and the price will be low, and you'll get 24kwh of batteries.
Looking on car-part, there's a Leaf pack from a wrecked 2014 for $2500 right now. That's $104/kwh.