Zyxel LTE3302 Battery Backup

[Dolby]

It was a tossup to put this post here or in the PC hardware - but this is regarding the power of the unit ...

https://www.zyxel.com/products_services/4G-LTE-Indoor-Router-IAD-LTE3302-Series/specifications

Anyone have any idea about the battery on this and what can be used ?

Battery (Optional)

• Removable lithium-ion polymer battery
• 3.8V, 2800 mAh
• Up to 4 hours operating time (depends on network environment)

It seems it's this - but not sure if anyone sells this locally?
Someone says maybe the old Samsung S3 or S4 battery?

https://www.amazon.co.uk/supplementary-Battery-compatible-WAH7706-WAH7706-ZZ01V1F/dp/B07GRYZSX8
https://www.broadbandbuyer.com/products/35088-zyxel-wah7706-zz01v1f/