I endorse psneeld and kchase.
We use a 'Hotpot' which is the same idea, fully insulated 850 watt heater, mixer valve etc
We bought ours from ASAP Supplies. firstname.lastname@example.org
I know they're in the UK but ask them if they have an agent near you, they have a 'can do' attitude so they'll certainly ship it to you.
When fitting be aware of the height of the top of your engine and the height of the calorifier, they need to be virtually the same to stop thermal circulation.