Amazon offers the Energizer Lithium Coin Watch Battery 2-Pack for $1.87. Add it to your cart via Subscribe & Save to drop that to $1.78 and bag free shipping. That's tied with our April mention and the lowest price we could find by $4.

Be sure to cancel Subscribe & Save after your order ships to avoid being billed for subsequent shipments. Meanwhile, Walmart charges roughly the same per-pack price with pickup, but you have to order a minimum of two packs.