Renata (the only maker) has ceased production of this battery (see the information letter).
The Renata 44 is obsolete and rare to find.
Closest size wise is the 346 (7.9 mm × 1.2 mm) .2 mm thicker and the lower voltage of 1.55 volt.
44, Renata 44, RT-44, XR710W,
not to scale.
Diameter × Thickness.
|Chemical Composition.||Nominal Voltage.|
|44.||7.9 mm × 1 mm|