Ebay, used. You'll pay about half what you will for a new one. Call up the person selling and assess them for their reason for selling and if they sound like someone who will have looked after the genny.
The one I sold recently costs £1,000 or so new and I sold for £359 on Ebay.
I was it's second owner and it had probably been run in total for about fifty hours, so it was almost new. Much better bargain than buying new.
Vin