Well the PSP isn't a popular system when it comes to covers, eventually someone will have it and it will pop up.
However if you can't wait two of those games, Rush & Infected, are fairly cheap on eBay brand new so you would be getting a fresh case, a crisp manual and a new copy of the game which in my opinion would be much better than just a printed cover.
And to make up for it, you could sell your coverless copies and maybe get another game or games in the process.