General things I get at amazon, for my cats (in addition to the l-lysine):
Krill oil. Good anti-inflammatory, food for coat and skin, heart, and immune system. I give it every other day though most cat people I know who use it give it every day
Amazon.com: NOW Foods Neptune Krill Oil 500mg, 120 Softgels,: Health & Personal Care
Egg yolk Lecithin, for hair balls. Hairballs are made up of fat and fur. The egg yolk lecithin breaks down fat, freeing the hair so it can be passed through the cat and out with the poop. I give a half capsule every other day for my cat who (used to have) a bad hairball problem, the other two cats each get a half capsule every four days, I take turns on which cat gets the other half
This is the brand I am using now:
Amazon.com: Egg Yolk Lecithin 600mg - 90 - VegCap: Health & Personal Care
but I intend to switch to this brand, because I think the "other ingredients" are better.
Amazon.com: Egg Yolk Lecithin 60 Caps by Swanson Premium: Health & Personal Care
Vet's-Best hairball relief. I don't use this product for hair balls, rather, I use it as in incentive dust, sprinkling a tiny amount over something they might be reluctant to eat. I relied on it heavily when making the raw transition. Now I mostly only need it for helping two of them finish up their krill oil. They do love it though. It is made with slippery elm bark, psyllium and marshmallow, comes in large tablets that are meant to be broken up (or made into dust, as I do).
Amazon.com: Vet's Best Hairball Relief Digestive Aid, 60 Chewable Tablets: Pet Supplies
Probiotic I had recommended to me, but I have decided to stick with the ProViable DC for now, which I get elsewhere:
Amazon.com: Natural Factors Acidophilus and Bifidus Double Strength Capsules, 180-Count: Health & Personal Care
Prozyme digestive enzymes. I probably won't continue using this. After 8+ weeks I am not seeing any difference or benefit.
Amazon.com: Trophy 454-Gram Prozyme Powder: Pet Supplies
PureBites freeze dried chicken breast cat treats. I use these sparingly, as a "chase the treat" game my cats love, and for my cat who sometimes needs a pepcid dose. I can give her a piece of the chicken, then mash the 1/4 pepcid into another piece and she eats it without noticing (most of the time), then another piece, to 'wash' it all down. One 1.09 oz bag lasts me about 6 months.
Amazon.com: PureBites Chicken Cat Treats, 1.09-Ounce: Pet Supplies
There are other things too, but they are related to raw feeding, not for general use.
**Disclaimer: I don't belong to any program for which I would receive compensation or other benefit by posting these links. I know Amazon has one, but I am not a member.**