If you need to replace your old toilet, you can buy new toilet from Costco store, which provides good price, and, their toilet package comes with everything for your installation, you do not have to buy small stuff like screws from another store such as Home Depot.
The Costco package include the Toilet, wax ring, toilet cover, stainless steel water connector, manual etc.
Yes, it was headache! There are multiple times when I bought Toilets from other stores such as Home Depot, Canadian Tire, I forgot to buy screws and wax rings or short water connector, I had to go back the same store to buy them.
Costco toilet package even includes the small rubber pieces and holders for water tank.
Anyway, when you buy toilet and you do not want to buy all other small pieces, please just go to Costco store, they have every thing in a single box, and the price is even cheaper.