If it is a 715cfm carb you can get one from Branda or Daytona Carb .com Holley does not make a kit for the 715 cfm any more.
If you are talking about the kit for the 715 (List 3259), I have used one available from Branda. Worked great. Along with the needles, seats and gaskets this kit included the secondary diaphragm and the gaskets for the fuel transfer line.