I have been looking for a Calorifier that would not cost alot and that was built to last. I found Surejust in the UK make an all copper calrifier complete with a NRV, 4Bar PRV and mixer valve and fittings. It comes with a 230v 1000 watt Immersion Heater.
I paid $823 for the 30l Surecal Calorifier and Expansion Tank, that included $57 shipping.
It arrived in just 5 days. Purchased through Heatso UK. I avoided PayPal as they wanted to slug me an extra $33 for currency transfer. No GST or Import Duty as under 1K.
Surecal Calorifiers are very well regarded in the UK, the last a long time if the PRV and Expansion Tank are maintained, no ferrous metals so an anode is not required.