Fasttech still has the glass for them, but not the complete tank.
They also have the mini tank (and parts) available. Get the "authentic" whenever possible. If it doesn't say authentic Kangertech, it's a clone and they often don't work as well as the authentic. (You'll probably be OK with the glass though.)
I love my STM's. I have 12 complete tanks and enough parts (using bellcaps) to make about 20 more.
Stock up now while you can.
Just did a quick check and found them in the US.
Kanger Subtank Plus Subohm 7ml Tank Set - $30.00 : Rocky Mountain Vapor, The Mountain top of Electronic Cigarettes
At check out, the code turkey get you 30% off.