Find a trade outlet that specialise in automotive paints, you may gave to drive a few miles to find one but they should be able to mix whatever you ask for. The aerosol cans have better nozzles too, to create a proper fan pattern.
For under £200 you could buy a small compressor and a couple of spray guns, that’ll give a far better finish. Spraying with rattle cans is much harder in my experience than using a proper spray gun.