I'm quite sure you aren't gonna get a set of them in white already, apart from ebay 2nd hand..... a bit of a gamble finish-wise as they'll have been sprayed up by gawd knows who. So that rules the second option out.
If you can live without the use of the bike for a few weeks, then why not prep the panels on the bike you're thinking of buying? Only takes an evening. Then hand them to any car bodyshop place you trust. As you'll be picking the shade of white, not colour-matching existing panels, this should be the most cost-effective way.
Cost wise - a few hundred for the paint and time. More if you want candy/pearls on there.