I would be tempted to do as Ben suggested and buy direct from China from an Ebay seller. The onyl thing to watch for when buying anything from overseas is gettign hit for VAT and import duty when it arrives. I've never bought anything of any great value from China (loads of low value items) so I dont have any experience of customs stopping stuff.
As to the panels themselves, I'm sure that they will perform within the specs, my only concern about the flexible panels would be the lifespan of the plastics used. But then for the application intended (on a boat) it may not be a concern if the plastics have faded in say ten years time.