Would China even want to sell it, even if they could? Letting a country stockpile doesn't seem in their interest: the whole reason you want to do it is to reduce reliance on them, they'd probably want to keep you hooked

We're letting them buy all our gold reserves and water rights (see alfalfa farming in the West), so everyone's got their price.

Question is whats more cost-effective: paying market rates to secretly stockpile, or paying for another Iraq or Afghanistan in the south china sea...