that bin kludge looks like it only stays on with the weight of the thing ,
no catch to use the part of the frame clip included for the purpose..
http://www.sjscycles.co.uk/brompton-...lat-prod13498/


the Bag Frame itself is available separately "£20.00"

taller, M bar
http://www.sjscycles.co.uk/brompton-...qfcfa-prod647/
shorter S bar
http://www.sjscycles.co.uk/brompton-...a-s-prod13499/