You can get pipe screens at any headshop.

Or, if you don't have one, go to a hardware store and look for faucet screens.

If you happen to be in an older washroom, pre-yr2000, feel underneath the faucet head and you should feel a screen. Those are used to catch any harmful grit that might happen to come through.

I hear newer homes don't have those anymore though.

Oh yes, and if you happen to get a screen from a washroom faucet, take a lighter and burn the screen a bit to kill all of the bacteria that comes through.