I got it (a long time ago) from someone who works in Thailand and he got it through his doctor, there it's normal, they give you prescriptions for as much as you want.
If you want, I can find out if the person is still working there and then I'll send you a message.
The only thing is that you have to send the money order, then he ships the meds (anything you want). I can also find his website possibly (I had it so long ago though..) so you can make a contact.
Let me know if you want me to try to see if he's still in Thailand.