Nintendo DS Touch Screen covers question?

I have just bought a Nintendo DS and iwant to protect the touch screen from scratches so i bought some screen protectors from Ebay.(Cheap ones) the first ones i got were ok,but after just one game the protector got so scratched up i could not see through it!I bought a 2nd set,but now with these ones the sensitivity of the touch screen is really reduced.I have to ram the stylus pretty hard for it to reconise touchs!Is there a happy medium or a product you or Nintendo recommends that will not scratch up and keep the things sensitive too?Please leave links so i can buy some!Thanks,Paul