According to Just Engines' website, Sig has signed a Sole Distributership aggreement with Irvine for the US, and J.E. may no longer be able to ship to the US. Someone might want to email Paul and confirm.

If true, this means you'll now have to buy them through a Sig dealer here in the States (unless of course you want to pay full list price and buy directly frrom Sig).

I've seen them advertised at some decent prices, though not as low as from J.E.

Read more:
http://www.justengines.unseen.org/USAfaq.htm