Here are some items you should keep around in case you need them. I'm a Girlscout - "It's better to have it and not need it than to need it and not have it."
Things you want to keep around:
Unflavored pedialyte for kids. You can get it in the children's aisle of the supermarket. This will help with dehydration. Like other electrolyte preparations, if it tastes good, you need it.
Imodium liquid. You will have to go the local full-service pharmacy for this item. You want the unflavored variety. This will help with diarrhea when other things don't work. Check with your vet for dosing.
A syringe without a needle. You can find this in some cooking stores, but the one you need is marked with cc or mL and can be found at the pet supply store or pharmacy. This item is for dosing your pet with liquid medicines and water. I suggest no more than 50mL, since anything larger coming at a sick cat tends to scare and upset them.
Hydrogen Peroxide, 3%, for cleaning wounds and stopping bleeding. It's great to have around.
Triple-antibiotic ointment. I suggest keeping some on hand for cuts and scratches.
Ivermectin 1% solution. I've found this in huge bottles. It's great to clean out the ears - and don't get it in the eyes. 1 drop in each ear every month. Try the local feed store, and I'll give links as I find them. It's made for cows, horses and other livestock. We are using the smallest possible amount for our cats.
Cider vinegar. It cuts fungus infections.
White vinegar. Clean urine spills. Don't use bleach.
Sterile bandages - strip bandages and pads. This is cheesecloth like material that is sterile for covering wounds. You also want cotton balls and cotton tipped swabs.
The beeswax impregnated tape that sticks to itself. It is sometimes called athletic tape. Don't use the tape with adhesive on it because it pulls fur off. This will stick to the fur too, but not be as prone to pull it out.
You will need an eyedropper. These are widely available at pharmacies.
DMSO - this is sometimes found in model and hobby stores. It is a solvent. Used on the outside of the body, it relieves pain. Do not give your cat this product to drink! Do NOT give your cat aspirin or tylenol!
This is all pretty generic stuff, and you may find other things your cat needs to have around. Anything that is hard to find will show up on this website, so just look around. You should find it. (hint: use the search function, below)