Hi,
thats funny,
the nature of a thing (user replacable)
doesn't change if you haven't found where to buy it
see
$7.87
Saflok- 54240 6V-Lithium-1300mAh-Door-Lock-Battery

the user has to do no soldering
If the connector is the wrong kind of connector,
just twist some wires together
but yeah, its highly advanced complex life saving device
that instantly breaks the second the original battery expires
:P