Threaded caps what size and where to buy?

[sledcrazyinCT]

OK I need to refurbish a couple gas tanks. I have not had any luck at the local depot or ace hardware finding a suitable cap that I can thread on to the gas petcock on a 350x and 200x tanks. Anybody have a source for this? I want to also try filling a tank with water to freeze out a knee dent and using a cork won't work and I am afraid using the fuel petcock and freezing could ruin it

So where can i get this cap or can someone confirm the size and thread pitch at least?

thanks for any info

[badass350x]

Run A rubber hose over the spout with a hose clamp, other end put a bolt of size in hose with another clamp. Done deal!!!