Available in various sizes at plant fairs and shows but do contact me to see if I have a little one to pop in the post. It'll be no more than £10 + £5 p&p

Iochroma  'Alba'

That's Iochroma with an I as in Iodine. Closely related to the Angel Trumpet Brugmansia, these tiny Tiny Trumpets are also from South America but are generally to be found at greater altitude  and are hence hardier and most species may be successfully grown outdoors in most of the UK. 

Iochroma 'Alba produces bursts of lovely little white flowers in clusters throughout the summer and early autumn. Popular with Bees too.