Hi there while a cool mist humidifier can be a great option in a room with a Cham cage just make sure you are not attaching this to blow into your cage during the day. The heat from the lamp and the lights with the fogger running non stop in a cage can create the perfect situation for the cham to get a respiratory infection.
As far as a drainage solution. You can either get a dragon strand drainage tray or get a hot water heater pan. Here are some links. Get the size that is appropriate for your enclosure.
https://dragonstrand.com/accessories/
https://www.amazon.com/DiversiTech-...SV2D0V11G1B&psc=1&refRID=48GR67TZ8SV2D0V11G1B
Thank you!!!!