Go on Amazon and search "Marine Heater", there will be a bunch of knockoff Espar d4 and d2's, all types of colours. Iv'e installed Espar heaters before, and these look exactly the same, heater housing is identical. Not sure if they are the same parts made in china, just not sold thru Espar, but wouldn't surprise me. For around $4-500 can't go wrong trying it out. If you have your heart set on brand name, look up Heatso.ca, they sell Webasto and Espar kits. Best prices you will find.
https://www.amazon.ca/Automotive-Fou...%2Bdiesel&th=1
https://www.heatso.com