EnGenius FreeStyl SIP2, Long Range, Portable 900 Mhz Scalable IP Phone with 2-Way Radio for Broadcast/Intercom, Expandable up to (10) Handsets per Base, 10 Acres of Coverage, Includes (2) Handsets (Amazon Affiliate)
US: https://amzn.to/3p6i2Cq
EnGenius FreeStyl SIP-HC Expansion Handset with Rechargeable Battery and Cradle, 900 Mhz Scalable IP Phone, 2-Way Radio for Broadcast/Intercom (Amazon Affiliate)
US: https://amzn.to/3rfB9wu