Not specifically.
Hein Gericke do a clear plastic protector sheet that you can cut to shape, I've seen it used on the side of the tank to great effect.
I would imagine that other suppliers will do something similar. eBay is a great source of this sort of thing, I did a search on 'Vinyl Sheet' and this is what came back ->
http://www.ebay.co.uk/sch/i.html?_nk....c0.m270.l1313
Generaly though, unless you are off-roading, it's pretty hard to scratch the tank on these. I've no protection and my tank hasn't suffered (other than a couple of offs in sandycrap where my boot tip made a couple of decent marks) from my knees.