This sounds like it's either a trade or a licensing restriction. Possibly the alloy is not permitted to be exported from Japan, or imported into the US due to US trade agreements, or licensing restrictions from the producer of the alloy. Or US trade regulations deem that either the alloy, or the kickstand itself can be used for other nefarious purposes, especially by terrorists. The classic example is large plastic tiewraps can not be imported/exported to/from certain countries because they are used as handcuffs by law enforecement agencies.

This is why I thought the same (or similar) kickstand might be available in the US but under another name, different distributor, etc.

Unless you have a friend who is traveling to Japan who will agree to find this for you, I'd set my sights on some other kickstand. The paperwork for the seller to ship such a small item legitimately will be more trouble than the thing is worth.