A genuine Harley tank comes painted, either in primer or colour-matched for a specific model and year, so unless someone has deliberately stripped the paint, you won't find one in bare metal. Reading the small print in the Ebay link it indicates that is Brand: Tucker Rocky. Certainly looks good and a snip for that money!

With patience it is possible to get cheap genuine tanks. I found a new showroom take-off on Ebay for 100 bucks a while ago, with a small dent - and that is a 6 gallon Touring tank.