You CAN get them seperately - you just need to find a GP or hospital willing to get them for you. You may also have to pay for them.
It is a HUGE PITA.

I have a doctor here who will do it, he is Pom who gets them from Europe, totally against the ****tail.
Im not sure if he would be any help for you, but if you pm me I will give you his contact details and you can see if he can point you in the right direction, or even hook up with your GP and go through him to get it