[oil pan 4]

An OEM style should be well under $50.
So I see you are in Virginia, so was I when I installed my block heaters.
I am convinced that if you go into any auto zone, advance, O'reillys in Virginia and ask for a block heater they will look at you like you are stupid.
"Because it doesn't get that cold here" (in Virginia)
The same thing happened to my friend a few years later when he wanted to put a block heater in his 4cyl Toyota Tacoma in Virginia, advance, auto, O' and even the Toyota dealer ship all thought he was crazy.

We end up going to Napa and they found it, they even had them in stock. If you go to the big napa.
For me Napa just happened to be the last place I tried, for my friend the nearest napa was a bit of a drive.

You can order them off the internet but all sources for my block heater I could find started at $50 and up then you still had to pay for shipping. These little block heaters should have been $25 to no more than $40.

Also don't be afraid to install more than one block heater if you have room.

Remember the faster you can heat the engine the less heat will bleed off into surrounding space.

Note:
My hot water heater element based 220 volt coolant heater can be built for around $25 and in wattages ranging from 1500w to 4500w. They can be used with 220 or 120 volt power, to run them off 120 volt power just multiply the rated wattage by 0.25 and you will get your wattage at reduced power.