You can get excellent pricing data from Heritage Auction's auction archive. You do need to sign up for a free account to see the sold price, but that's easy and they won't spam you.
I searched on Kelley Jones and they've sold 15 pieces of his art. In June, they sold one you might have liked.
I've never done it, but you can send a note to the owner and make an offer.
Next up, Market Data on the CAF. It searches Heritage plus eBay and a couple of others. You need an account (free, no spam) and you will need to subscribe to go back very far, but it's not terribly expensive.
Google tells me that the Art of Comics has pages from Red Rain.
Dragonberry maintains a list of art sources. This OA board has a marketplace section that has a dealer list. You can also post a WTB for such art.
That ought to get you started.