Amazon offers its Prime members the Sanyo Eneloop 800mAh Pre-Charged Rechargeable AAA Battery 4-Pack, model no. SEC-HR4U4BPN, for $7.99 with free shipping. (Non-members can spend $25 or more to qualify for free shipping; otherwise, shipping costs $5.74.) That's the lowest total price we could find by $2. They purport to maintain a 75% charge after 3 years of non-use.