You can buy solar salt at Home Depot or Lowes, that's the salt that is used in salt-based water softeners. Works just fine. However, the pool stores will all tell you that is cheap salt with lots of contaminants and it will destroy the SWG so, at the very least, please buy our very over priced 40lbs bags of pool salt...
I understand you need some help getting the cell installed but have you tried calling around to pool builders and asking them how much they would charge for a cell and install? Pool stores are notorious for selling equipment that is highly marked up and charging A LOT for labor. See this chart for a comparison of SWG's -
Compare and Review Saltwater Chlorine Generator Prices and Features
Ideally you want to buy one of these systems yourself and then find someone to install it. You will pay a lot less for an SWG (and get a better quality unit) by not buying some rebranded model at a pool store.