Whatever works for you. :) Personally I'd rather go to the dentist than WalMart.

Kirkland batteries are also available on Amazon...

https://www.amazon.com/Kirkland-Signature-1-5V-Alkaline-Batteries/dp/B003FZ4RQA

They are more expensive there though (I think they are $11 at Costco vs. $22 at Amazon). But probably still cheaper than 48ct. Duracells.