That metal plate does hold up your tank. I would be talking a good look at it to make sure your tank is not going to come loose. Take a good look at the tank as well, I've sold many gas tanks for 1999-2002 Sportage's.
A new shield is not to bad, brand new from Kia, list price is $166.00, I could sell you one for $130.00...shipping would be a lot though. If I were you I would just go to your local Kia dealership and order one from them.