Another block heater cord thread

[OM617YOTA]

PHOTO ADDED BELOW.

Howdy folks! I checked the cold starting links at the top, didn't see this mentioned.

I have a stock factory MBZ block heater in my engine, it came without a cord. Bought the Kats replacement block heater cord. If I push very very hard, the cord will insert into the block heater and as long as it's inserted as far as it will go(which does not appear to be as far as it SHOULD go, the plug does not appear to seat), it will turn on and heat. Wiggle the cord or the engine ever so slightly(like a cat jumping up on the fender) and the plug backs out a teensy bit, looses connection, and stops heating. Wiggle the truck a little more(like the cat jumping off the fender) and the plug comes out entirely.

I don't trust this thing to keep a good connection and operate unattended. If the worst it would do is maybe not heat the block, I'd say OK no big deal. I am afraid it would burn my truck down.

What's the best source for an OEM heater cord, and who could I beg or bribe to post a good photo of their block heater plug? I would like to compare how far the plug goes into the block heater on a good solid working model vs. my intermittent issue.

Any other ideas or tricks? Thanks all.