There is a thread about some new aftermarket boosters from Vick Auto giving problems. I would take my chance on a likely good used one. are you sure that the leak is not between the booster and the plastic connector for the hose?
85 GTV6 3L
76 Suzuki GT500
2011 Jaguar XKR
A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke