I'm in the US, btw. Thats all! Actually, if anyone has heard them I'd love some feedback. Debating between them and GR07.
Here's the thing about the j-phonic : Being a semi-custom IEM, it's made-to-order only so even in Japan, you'll rarely find it in a brick-and-mortar shops.
If you're lucky you will find 2nd-hand unit in a brick-and-mortar shops like e-earphone or fujiya avic, but this is a pretty rare occurrence. If you find it in e-earphone or fujiya avic, even rudimentary-level Japanese would be useful since the employees working there barely speaks English.
The easiest way to get it is through ordering from jphonic's own website. Sadly they no longer have English site though, and as tomscy2000 said, they don't ship overseas anymore, so you'll need a forwarding service such as Tenso or a proxy to get it.
You can have it shipped to proxy companies like Tenso, who will then forward it to you. A hassle, but not like you have many other options anyways...
I checked e-earphone's newest 2nd hand listing; They no longer have j-phonic k2 sp :/