I buy the 10 lb. size of CYA at Amazon which is currently shown as costing $25.
I buy baking soda at Walmart, Muriatic Acid at either Home Depot or Lowes. Pool salt at Walmart, and Calcium Chloride (20 lbs. for $26) at Amazon.
I have a cartridge filter and buy replacement Unicel cartridges from whoever is currently offering the best price.
I have an SWG but keep a couple of gallons of bleach on hand. I have bought it at various retailers who sell 8% or 10%.
And test kits and supplies from TFTestkits.com.