Block heater in Canada is almost as popular as tinted glasses or A/C in the US.
Any auto-parts store or car dealer have them in stock for most cars.
For a 103 engine, retail price at Benz dealer is $Can42.50.
I had one installed on my 1989 260E about 10 years ago. I also have a temperature activated electrical switch and timer(110Volts) that will activate the block heater if
a) temperature falls below the predetermined temperature (in my case, I choose -10C) or
b) at a pre-determined time of the day/night.
There is no reason to use the block heater at higher temperature or all night. 2 hours before start-up is enough.