Here's that Sporty tank I have. No leaks. Been using it since 2009.
Comes with a cap but no petcock. 3/8" FIP bung for mounting the petcock.

http://s414.photobucket.com/user/rakentrail_photos/library/Bobber?sort=3&page=1

Remember, if you can't be an athlete, you can always be an athletic supporter.