I have made a bunch of these and Yes The Firestone works the best.
Go to http://www.beverageequipmentco.com/Home_Brewers_Kegging_site.htm
See Item # 55542
or
http://www.beverageequipmentco.com/Beer%20Line%20Sanitize.htm
Item # 55143
:D It is in the Cleaning equipment, I call and they are addind it to the Home Brew Parts section all so. I was wrong on the price. it is $19.99 here is the link
http://www.beverageequipmentco.com/Beer%20Line%20Sanitize.htm
http://www.beverageequipmentco.com/Home_Brewers_Kegging_site.htm
I found this same unit @ a company called 'Beverage Equipment.
Werd. I bought one and it works Great. $ 21.99
It was about the same to order the Firestone fitting and make it.
www.beverageequipmentco.com