Yeah, you are right about it just coming down to max safe chamber temp. For those interested these are the components I have bought to run a separate heated chamber:
Heater: ￡10.54
https://a.aliexpress.com/_mr8BEEA
(I got the 24v 250w but I have a spare 24v power supply. You could go 12v and use a regular power brick or even 120/240V and run it off the mains. It depends on what wattage and power sources you have)
Temp controller: ￡3.26 12V 24V 110V 220V Professional Digital LED Temperature Controller
https://a.aliexpress.com/_mP9cJx4
This is pretty simple electronics, it has a temp sensor and is wired into the heater power delivery. You then set a target temp and the device turns the heater on and off to hit that temp