Looks like you're in the UK, but www.logees.com sells it.

On 21 Nov 2003 04:16:51 -0800, (Mark Fawcett) opined:

Can anyone tell me where I can get seed for Strobilanthus dyeranus,
more commonly called Persian Shield. Ive seen pictures of this plant
on several US sites but not in the UK (where I live) and I would
really like to grow it. I understand its probably going to be frost
tender where I live but I have room to store it over winter.

thanks

Mark