I bought this off amazon for $20.24 and it works perfectly. Unfortunately it doesn't come with the end prong cover like the original did.

Zerostart 3600001 Auto and Light Truck Replacement Cordset for Freeze Plug, Engine Block, Oil Pan, and Transmission Heaters, 5-Feet | CSA Approved | 120 Volts

The block heater now seems to work. I used my infrared thermometer and aimed it at the connection to the block and within 10 seconds it when from 60 degrees to 90 degrees. It's not really needed right now but I will be using it in a few months.

I need to also adjust the valves and check the glow plugs. I'll do a compression test when checking the glow plugs.