My bad. I had incorrectly assumed the sensors were all ZigBee or Z-wave.

It does look like you can buy 433 Mhz signal amplifier devices. Here's the first one that popped up on Amazon for me

JC Wireless 433Mhz Signal Amplifier Repeater for Alarm System https://www.amazon.com/dp/B07JNSHL8Q/ref=cm_sw_r_apan_glt_fabc_EPH77S8PG70Z1QPA4C16