Don't mix brass with aluminum as others have said. You'd be better off with a steel or stainless steel plug in a pinch. As others have stated, go to your local hardware store or home center and pick up a new nylon plug. You could probably use CPVC as it's rated for hot water use.
I used to work in a plant that made air con tubing and heater pipe for cars. They were so concerned about dissimilar metal issues that they wouldn't allow brass and aluminum fabrication operations to exist in the same building.
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