Insurance for Borrowed Bike UK/USA/Canada - Advice Please
 

First, let me say I've searched the threads, using the 'search tips' but can't seem to find anything specific for wwa I need. Second, I hope the post title is clear and that it's in the right place.

I'm from the UK, planning a trip to the USA and Canada next year, flying to the USA and hoping to use a 'borrowed' bike on a trip exchange basis for the trip. The bike will be registered to a US citizen and fully legal.

My question is about finding a suitable 'temporary' (as in 4-6 weeks) insurance policy. So far, I've not managed to find anyone who can do it (latest being 'Progressive' - who have been mentioned a lot on other related threads). I'm not entirely sure at this stage whether I should be getting it from a UK based company or from a US one, though I think it likely to be the latter.

If anyone has done this or can point me in the right general direction I'd be very much obliged.