The low capacity of rechargeable lithiums just don't make them very caver-friendly at this point in time.
Your best bet would be to order batteries in bulk instead of buying them in a store.
These people have treated me very well and have good prices (and free shipping):
https://www.fenix-store.com/index.php?cPath=53_59Your other alternative would be to sell the Pro and get the standard Apex that can take rechargeable AA's.