My radiator leaks steam. I closed the supply valve and the leak stopped, so I'm under the impression the graphite packing, beneath the packing nut, needs to be replaced. Upon removing the packing nut, that sure seems to be the case.

I bought new graphite packing but when I attempted to tighten the nut I stripped the threads. I don't know if I stripped the threads on the supply valve or on the nut itself, but rather than buy a new supply valve and go through that hassle, I'd rather try to find a new packing nut and try that first.

I'm having a challenge finding this packing nut, though. My local home stores don't offer it and I can't seem to locate it ******. The nut measures 1" in diameter, if measuring from the inside of the nut, from thread to thread. It measures 1.25", if measuring the diameter of the outside of the nut.

Does anyone have any advice?

Here are pics: