Fuel injection pump thermostat housing.

[Ozone]

So mine had a few holes that could not be patched. The replacement (aftermarket, OE is NLA) is $125(lowest I could find).
It is a steel tube with a cap, two fittings and a flange. Zinc plated steel, not even stainless. $125 to $250, depending on where you shop.
The price was the motivation.
The plan is to make one out of SS 304 round with dimensions close to original.
This one is a crude prototype to run while I wait for material.

[Cees Klumper]

I applaud your tenacity ...

[wwheeler]

You must have a machine shop. Clever.

[Ozone]

Fortunately(or otherwise) I have access to a machine shop and some training. I did not have a drawing, just an idea of what it should look like.