Here's a site that has compiled a
chart of online sources of Rush and other "popper" type products.
Being one of the oldest brands, Rush has been so widely faked and counterfeited that the specific formulation you liked might not have been genuinely-authentic. Besides, formulations have changed so many times that it's impossible to define exactly which variant ought to be considered the "authentic" formulation. AFAIK there's nothing like the oily yellow variant from around 1990, for example.
Your profile says you're in Oregon, where stores only seem to carry isobutyl nitrite formulas. If that's not your preference then try
minotaursf for a product that's distinct from the current store brands, or search the Czech
Amserdam-poppers for a painfully-confusing array of differing formulas.