Anyone have a source for Librem 15v3 or 15v4 batteries?

Librem 15v3 and 15v4 take batteries that are sometimes referred to as U753-TS44-111, but they seem unavailable. Does anyone know where one can be had?

Batteries Plus+ Bulbs?

And if they find it, maybe they can also put a warranty on it? They did it with my Timex watch and battery replacements are free. (When I mean “maybe”, their policy for laptop batteries may be different.)

Noticed them at the Purism store recently…

Those are for the Librem 13. The correct one for the Librem 15 is below.