Mortons has curing salt in every store I've ever been in. Its all pink for identification.
I already have Morton Tender Quick. It has 5% sodium nitrite, 5% sodium nitrate, sugar of some type, and the balance of salt and some other stuff for caking. What I want is pink curing salt #1 aka Prague Powder #1 which is 6.25% sodium nitrite and just salt for the balance. All the recipes I've seen say you only need a very small amount of it per pound and you can use however much or little kosher salt and sugar as you want after that. That will also nip the saltiness of our pastrami in the bud (I think).