I think it's best to buy the individual things rather than a full kit, that way you can get what you really want/need. There are lots of online animal pharmacies which often work out cheaper for most 1st aid supplies.
I was going to ask human or equine. If it is human, I have a list of things I must carry as a ride leader, inc a space blanket and a soft support for a broken arm, as well as creams etc.
I like to keep things that do both horse and rider. Agree with post it is cheaper to buy what you want.
I get a lot of my stuff from Claytons First Aid such as Primapore - like giant sticky plasters! Stick well to horsey fur, and comes off without giving them a scalping!
They're a humans First Aid supplier really, but sell all the sorts of things I use on the neds anyway like Hibiscrub, Sudocrem and the like.
I've just got a load of bandages etc from www.horseactive.co.uk, ordered late on Monday night, arrived yesterday - very prompt service. They do all sorts of things, including first aid kits.