Here's the thing, your going to go out and play kitchen chemist using a lot of products that you don't know what else is in them to try and save some money. In doing so, you'll also put your tank at risk. All you need is one item that isn't safe and you just wiped out your tank.
In addition, you'll spend a lot of time tracking all this down.
While you many not like buying online, it really is the best solution. You place the order, wait a few days, and it arrives. You'll have exactly what you want, and no risks to your tank.