Well... as above, I refuse to pay £288+ VAT so I ordered a pair of replacements from China via eBay.
They arrived today, earlier than predicted and so far look pretty decent for the 20 odd quid I paid. They have die cast bodies which look very much like original Japanese manufacture, but may well be pretty decent fakes. The way I see it, it's difficult to go wrong for the money.
Of course fitting is the next thing. Being prone to provoking balance problems/vertigo, if I so much as bend down, and also having both knees so knackered that bending down is inadvisable without a very comprehensive plan for how to get up again... I shall probably put the task in the hands of my local mechanic/MOT guy.. who is also a Honda lover/owner.