Car undersealeant from retail stores

[PESKYWAABBIT]

Could anyone recommend me a car undersealant that can be purchased at usual retail shops. Just got myself a Japanese import Subaru Impreza and the British roads are laden with salt at the moment. Can't hang on too long as the undercarriage of the car is MINT and I want to keep it that way.

Need some that will last for months if people know of one. Needs to be one that can be applied without a compressor. Cheers peeps