I've just ordered a couple of screen protectors on TradeMe: http://www.trademe.co.nz/Members/Listings.aspx?member=3254177. $1.99 each and cheap postage in a fastpost envelope.
Each comes with a cleaning cloth and he put up a different multiple unit auction straight away when I asked as there were only 1x or 10x listings. I've just ordered 2x so hopefully will arrive on weekend.
BTW, just comparing my clear TPU case with my trusty old LG500 Optimus and if I hold it sideways I can see that the SIII screen footprint will be about twice the size - really looking forward to getting my hands on the phone now!