Have you tried Chewy.com? If not, there is a fantastic deal available. You can get 40% off your first Autoship order.
I have used Chewy many times in the past. It is an online pet retailer with all sorts of pet supplies like clothing, food, treats, medication etc… We use Blue Buffalo dog food for our dogs and we go through tons of the big heavy 40# bags. I was buying at Costco and then switched to Amazon because the price was comparable and I liked the convenience. I discovered Chewy was the same price as Amazon and they offered a promotion similar to this so we switched. My orders typically arrived very quickly- unlike Amazon which takes ages these days.
The offer is for autoship orders so you will pick a schedule and get a regular delivery of your items. You can cancel that at any time you want or suspend orders or increase them– whatever.
The offer is up to $20 off and shipping is free on $49 orders. They do have great deals on toys and gear for pets too. My orders were usually not quite $49 so I always added something to the order each month to hit that price.