Thanks for the additional details.
I’m currently in Chile and local battery distributors here generally suck, haven’t found a good one yet, at least for Li-Ions – if you have a reseller or similar here, please let me know.
In the US I usually purchase from illlumn.com and other stores listed on batteries.parametrek.com – alas, I see the N40 isn’t being listed, probably because no stores are carrying it yet… @Parametrek might be interested to hear from you when you have any stores selling them.