Best is to buy the first aid stuff separately, alot you can get from the chermist or pound shops. Buy yourself a cheap plastic tool box to put the things in.
vetrap or similar, gamgee, lint, cotton wool, hibiscrub, scissors, electrical tape (always useful) stainless steel bowl, bottle of sterile water, sudocrem, vaseline, latex gloves. syringe for washing debris out of cuts. There are probably other things but that lot will give you a good start.
ditto what T_Z has said about buying it all seperately - will work out way cheaper.
off the top of my head in mine ive got:
metal bowl, lots of cotton wool, gamgee, bandages & pads, vetwrap, scissors, thermometer, syringe, blade cutter (for taking stitches out) saline spray, tape, glue, gloves, bute, vaseline, wound cream, sudocreme and vaseline, hibiscrub.