If you live in rural America you have a treasure trove of preparedness supplies within arm's reach at your local feed store or farm and ranch supply stores. Some of these goodies are outdoor supplies like fencing and water tanks. Many of these stores are also a significant source of medical supplies at a reasonable cost. A sterile syringe doesn't care whether a horse or a human uses it. Neither does betadine solution or an ace wrap. Our local Feed Store has 2 kinds of betadine solution -- one that foams and one that doesn't. They also carry about 8 sizes of syringes -- I use these a lot for giving the dogs liquid medicines.
At my local feedstore I found a bottle of 100 amoxicillian capsules at the 250 mg strength. Those could come in handy in an emergency.
Here's an interesting product that is little used these days: Ichthammol. After reading about it, I went looking for some. Some drugstores have it behind the counter, but at a low percentage strength. Feedstore has it at 20%. I use it for tough-to-get splinters. Slap some on under a bandaid before bed, they are easier to get the next morning. There are other human and veterinary topical uses for it.
In the horse area, I also found lots of great colors and widths of the 3M sticky wrap. I guess it's great for taming the wild horse tails during parades and other events. Could be helpful in an emergency, too.
The items pictured above cost about $35. Add a pint of betadine and you could still get change from a $50 bill. I think I'll poke around at the new national chain pet store soon to see if they have any offerings for the first aid kit!