Mark:
You can buy this from Defender.com, search for a fuel tank vent. These are the ones used in my sewer vent line by the factory.
They are made straight or 90 degrees, mine is the 90 degree one that looks like this.
Whitecap Fuel Tank Vent with Wire Screen
Type: Angled (90 Degrees), Material: 316 Stainless Steel
Applications: 5/8" Inside Diameter Hose, Hole size is 3/4"
Commonly Used on Fuel Tanks but will Vent Any Tank
Link may not work or may change
HERE
Hayden