Luckily for you, I already have several gaming networks as custom profile fields on my site...
PlayStation Network ID
Max length of allowed user input: 16
Field Length: 25
Official PSN profile page link: http://us.playstation.com/playstation/psn/visit/profiles/TwilightLynk
So basically, I would enter "TwilightLynk" into the field and it would generate that custom URL where ever you want to place it as...
PlayStation Network ID: TwilightLynk